should I be concerned?

So I recently got back together with my ex and things seem to be going good see each other quite regularly he compliments me lots etc etc but I've noticed he keeps liking his ex girlfriend's (not really serious think they were just sleeping together for a bit) instagram pictures and I can't help but let it bother me. It's a mixture of pictures of scenery or of her and her friends and even a bikini picture.. He likes quite a few girls pictures celebrity's and his friends which I don't mind but ex gf pictures I feel uncomfortable with and I'm generally pretty chill.

Question is do I bring it up and ask him about it or not and if I do how do I without giving off needy/controlling vibes? And is it something to be worried about or not? Because personally I see no need to be in contact with an ex in anyway unless you're good friends which I don't think they are.*

To be honest, it could be nothing. You should bring it up in a joking way and see what he says. I honestly don't mind when my bf like his ex's pictures but the bikinis ones might be a red light.

I'm curious: why did you break up with your ex in the first place and what's his relationship history like? Does he have a history of short-lived relationships?

I'm a girl but this is why guys hate girls, we think we own them and can dictate who they fancy! Double standards, a guy so much as says he fancies a girl even if he's single and he's a criminal a girl can do what she wants and dictate who a man can like

Because we both had final exams and we hardly saw each other and it seemed like I was the only one trying to make plans to see each other. He does but not ones where he's introduced them to his family like he has with me.. If that even means anything.*