Obsession over long lost ex

[Thebigregretter]

I am pretty sure I’m being ridiculous and maybe even having some sort of mental breakdown type moment but I really can’t admit any of this to anyone so here I come to Mumsnet for someone to hopefully talk sense into me or help me see things more clearly/help me out of the obsessive cycle I have found myself in.
Life has not been great for a long time now. Relationship is awful, at times if I’m totally honest abusive (hence why I can’t confide any of this in real life friends). Totally trapped by a combination of having two young children one of whom has SEN and is extremely full on, a mortgage which OH has already threatened to stop paying if I end the relationship to basically ensure we both “lose it all”, I have no family to help me with any of this and am just about keeping my head above water with it all.
When I think back to previous relationships the only regret I have is not binning them off sooner as none of them treated me particularly well. With the exception of one, someone i haven't seen in almost 20yrs and who I have always wondered about over the years and have regretted how I treated him. Sheer nosiness initially made me look for him on social media where he has absolutely zero profiles or presence on anyone else's profile, I found a couple of his family's profiles but nothing much on there other than I ascertained he had a son 13 years ago, no actual photos of him etc so in my thoughts he has always remained the 23yr old man I knew and loved.
As life got unhappier my thoughts returned to him and the urge to know more about him grew, if I’m honest it gives me comfort sometimes on my darkest days to fantasise that I might find him and we rekindle things, I do recognise I’m being absolutely ridiculous but I couldn’t put him out of my head and started to think I really need to see something to show me that he’s not who I've built him up in my head to be, has now also aged/isn’t the same person etc so eventually my digging went a little deeper and I found him on an electoral roll that he was until recently living in a one bedroom flat which to me says he is no longer with his son’s mother. After years of absolutely not a single photo etc on Facebook from anyone who knows him, and I’m ashamed to admit I have spent hours trawling through profiles to try desperately to find him, I completely unexpectedly saw a photo of him yesterday. 20yrs older, but him. Definitely him, with a guy I remember him hanging about with when I knew him. I cried when I saw it after all this time wondering about him. This has totally thrown me. Why have I now seen this photo by chance? After years of wondering about him and actively searching for him? Does this mean something?
I’m going to be brutally honest and say the rational part of me knows my own life has become so miserable that I’m becoming obsessive about what I perceive to be my lost chance of happiness etc and am acting a bit nuts. Even if I were to miraculously track
him down somehow, WTF am I actually going to do? Stake out his home? Then leap out of the car at the first sign of movement and apprehend him, hoping he will be overjoyed to see me and we will…..do what? Leave my horrible OH and totally uproot my kids? Hope OH doesn’t actually commit mortgage abuse? obviously none of this can ever actually happen but I feel this sad, desperate urge to just see him. To feel how I felt when I was with him again. To feel like there is someone out there who is right for me. It’s all crazy and I know I need to stop this constant obsessive thinking about someone who I haven’t seen in the best part of 20yrs and who probably has never given me a second thought and would be horrified if he thought I had actually been obsessing about him like this (obviously I’d never actually admit any of this to him or anyone I know in real life)
I guess what I’m asking is how do I stop
this? How do I stop the constant regret I feel and longing for another chance at life? How do I stop acting so deranged? I know
I'm not behaving normally.

That should read fade and disappear. Typo.

Thanks for your replies. The sane part of me knows it’s ridiculous to think I could ever think I could randomly appear at his house etc and expect him to be anything other than creeped out that some random he went out with years and years ago has gone to all this effort to track him down (mortified at the reality of what I know the reaction would most likely be even though obviously in my daydreams we live happily ever after) and even if he were open to seeing each other again, I’m in no position to realistically be entering into a relationship while navigating what would I anticipate would be likely to be an extremely stressful, horrendous split from OH while obviously trying to protect the kids from it all, there’s no way I could ever actually start a relationship with anyone amidst all that. And let’s be honest as if the long lost ex or anyone else would think I’m a catch, I’m in my early 40s so looks wise past my best, two kids one of them who has SEN and requires alot of supervision/is very full on, horrible OH lurking in the background forever more, small matter of no current financial independence - what man would walk into that mess? FFS I feel I’m often on the verge of boarding a train and disappearing from it all so no way he would want to be part of it voluntarily.
Thanks for advice re CAB/women’s aid, I will follow this up once the kids are back at school. Also planning on forcing myself to implement some daily exercise into my routine again to try and give myself something else to focus on.
I hope it helps shift my mind away from ex. I would currently do anything to spend an afternoon with him even if it were just to see he’s turned out to be totally different to the image I have in my mind of him and completely turns me off him (recently found photo says otherwise; he has aged really well 🫣)

Life won't be like this forever, you can divorce and he will likely not want to be involved with the kids. 2 kids is very common as are SN. I think it's depression making you feel stuck.
Your crush that you see as great might have ED, financial troubles, baggage from exes.. everyone has baggage by 40 😉

Someone better than your obsession might come along but you need to be in a space where you can actually date and emotionally ready to try again. You might live 50 more years, don't give up this is just a shit time and you can get through this but do so in health way. Your plan sounds good so hang in there and keep digging your way out. Fantasies keep you stuck. Make your reality so great you don't want to escape it.

He could be living in a one bed flat because he stopped paying the mortgage on the family home as punishment for his wife deciding she wanted to divorce him.

Which means that, instead of being the gallant knight on a white steed/Ford coming to rescue you to be powerless and helpless under his management instead, he could be a faint light on the horizon telling your subconscious that it is possible for you to get your abusive partner out of your life more easily than you think.