I feel your pain. I've been there and am only just coming through the other side.
I was with my ex for 2 years. Because of prior heartbreaks and bad decisions (on my part) I took my time and trust was eventually built up. We both had barriers but grew close and made ourselves vulnerable to each other. For the first time ever, I truly liked the woman I was around this man. I respected him. I trusted him. I loved him. I saw a future with him. Then, out of the blue I received a text at 4 am, where he ended it then blocked me. His excuse was his depression and that it wasn't fair. We both suffered from depression but I help myself and recognise the triggers. He tended to push me away. But we'd agreed to try to work through this and had strategies in place. He obviously didn't stick to what we'd agreed. We met up and talked through it as I needed and deserved closure. He continued to harp in about his mental health, there was no cure etc. He said he was getting counselling for relationships.
We continued to talk for months after this and even met up for a meal. We were growing close again and out a stop to it. He knew I still loved him. He always used "friendship" as a way of keeping me on the back burner. Not this time.
During lockdown, I stupidly messaged him. We continued to chat and for almost 2 months. His behaviour grew suspicious so I did my "research." It turned out he was in another relationship and never mentioned it to me. There was no break from me to her. I spoke to her. She didn't even know about my existence. She told me he seeing someone else when she met him but didn't tell her, she discovered this herself. Then contacted this other woman, as I had her.
So, it turns out..... the man I loved with all my heart.... who I'd taken time to get to know.... to trust..... to let down my barriers with...... who I thought was the kindest, genuine man I'd ever met, who just had mental health issues was a vile, narcissistic abuser. He cheated on me with 2 other woman and I'm sure there'll be more. He emotionally abused me with his bullshit and did the same to the woman he moved onto. I then found out he also physically abused her..... she did it to him too.
I was literally floored when I discovered the person I loved was a total stranger. I felt utter disgust at the thought of him cheating and hitting another woman. I've been abused in both ways before and honestly would never ever have believed he would cheat or lay his hands on a woman. I was sick several times after his current partner (ex) divulged it all to me.
However, as bad and traumatising as it was to find all this out, I'm so very glad I did as I now know the truth. It disgusts me that he used his mental health as an excuse for his cheating, when he knows I suffer too. Too weak and spineless to admit the truth. Too dishonest and sleazy to be faithful. Eugh.
I'm left picking up the pieces and gaining my own closure. His current partner dumped him after speaking to me. But she thanked me for letting her know about him trying to reel me back in.... and about my actual existence!
Speaking to friends as helped the most. Being in here and reading others tales as too. It's good to think we're not alone. Yet shit to realise there's a lot of vile people around who thrive on manipulating and abusing good honest people.
Keep talking.... sorry for my ridiculously lengthy post but it feels so good getting it out.