My ex still affects my mood...is that bad?

So I dated this guy my freshman year (not long, 4 months only but he I fell so in love with him) and I’m in a new relationship with this guy and it’s almost been two years. But every time I see a Snapchat or picture of my ex with his girlfriend (who is my friend, or rather “friend”) it just places me in a bad mood. Not for a whole day but maybe like half an hour. I mean my boyfriend is great and I don’t have feelings for my ex but I feel guilty that I let him affect me. And I don’t want to tell my boyfriend cause I feel like he’d think I’m still attached when I’m not. I can’t even talk about this with my friends because they all like him and think he’s a sweet guy, when he was an emotionally abusive jerk to me. Is it wrong that whenever I see him being happy or even just a random picture of him it affects me? 😣😣😣😣