Not sure what I'm expecting from posting this, it's more of a vent as I have no one to talk to about it in real life and I need an impartial outlet, so sorry for the bumbling crap I'm about to spout.
A few years ago I had an almighty, all consuming crush on an acquaintance who happened to be a good friend of my ex (DS dad). I was single at the time but he was with someone so I did nothing about it. I had this whole obsessive fantasy in my head for the best part of a year and would literally cry some nights about the fact we wouldn't be together 
(I do suffer with attachment/rejection issues which I think is why I develop such intense crushes). I didn't have much contact with him, we would occasionally see other out but never exchanged more than cordial conversation. I finally snapped out of it around the time I got my current DP. I still saw this friend occasionally but it never escalated past fleeting butterflies.
This was 3 years ago. For background, my relationship wasn't great the first year and we did split for a while but we got back together last year. It's been wonderful and he has truly been amazing to me, I finally feel secure which is no easy feat as all my other relationships have frankly been shitshows. I don't know if it's a sudden fleeing response I'm having to DP being quite vocal about our future together lately.
This weekend just gone we went to an event that this friend also attended. I was talking to my best friend about this last week and she spoke about this other man going, about how gorgeous and nice he is etc.... when I told her we had spoken about it, she suddenly got defensive saying she hopes I mentioned DP which of course I had as we were going together (I've never cheated or anything like that but she does jump to conclusions and knows about my previous crush) hence why I'm reluctant to speak to her about this, and my other friends too as they know I once fancied him and none agreed with me taking DP back.
We didn't see each other but this whole weekend this man has suddenly been messaging me, still polite chit chat but more conversation than we've ever had - and my stomach is in knots. FYI nothing flirty, I've not hid my phone or deleted anything, DP has been right next to me and probably seen the conversation so it's nothing like that nor will it be more than that. I have no intentions acting upon this, but I can't help these frigging butterflies and have not been able to get him out of my head. I was already a bit nervy about seeing him this weekend but these intense feelings have erupted from nowhere.
We only bump into each other a few times a year, we don't usually speak so he's easy to avoid, but I don't want to end up down a rabbit hole like before or start resenting/disliking DP because I'm distracted. He's just messaged me (only asking about the price of something) and my stomach is doing somersaults, I'm certain he's not interested but I feel like a giddy school girl. I'm almost 30, I need to snap out of this!