DP and I have been together 18 months. At the beginning of the relationship it was long distance and we only saw each other every couple of weeks. This led to us breaking up 9 months in. He instigated it because he said he was struggling with being so serious about someone he couldn't see that often and he'd basically met someone through work where there was the possibility of it developing into more than a friendship and he wanted to be honest with me about that. I was heartbroken, angry at him, but at the same time I understood that the distance wasn't sustainable.
After 3 months he said he'd made a terrible mistake, loved and missed me and would move to my town so we could try again, if I was willing to. I was very cautious about this, but he did move back, we started spending time together and he has been nothing but loving and committed and our relationship is great. I love him very much, but after being rejected by him once I struggle with trusting in what we have. There's a part of me that, no matter how great it is, is waiting for the other shoe to drop.
Anyway, he was out with friends tonight (we don't live together as I have a child, so am very cautious about that). I was messing about on Instagram looking for new people to follow and clicked on the 'following' link, where you can see the activities of the people you follow. He'd just got in (I know as he'd just messaged me), and I could see he'd in the last 5 minutes started following a woman and liked one of her pictures. From checking her profile, she's a friend of his friends he'd been out with, so presumably he'd just met her when they were out. She's pretty - very much his type from what I can tell - and the photo he'd liked? She's in the bath, obviously topless. It's all very arty and tasteful through filters (which he'd like), but it's basically a selfie in the bath.
Given our history and the 'getting close to a friend' before, I feel sick. From the timeline I can see he did this before he'd even answered the message I'd sent him (he always messages when he gets in), so basically it was the first thing he did when he picked up his phone when he got home.
I don't know what to do. I'm second guessing myself because I know i have trust issues because of our history, but even without our past I'd be pissed off about this. But if I say something it also means saying I 'snooped' into his Instagram likes, which may make him think I'm constantly checking on him. (I'm wasn't, but I know I bloody will be now).
I'd really appreciate anyone's feel for this type of behaviour and if I should say something to him or bide my time a bit.