Need advice

Okay so was chatting my bf yesterday and he told me he might feel a bit weird today because it’s his ex gf’s birthday. And they broke up a year ago and we’ve been together since April. I don’t know but is it okay for him to feel that way cuz I don’t think he should. We’re in a relationship and I don’t think it’s cool for him to have such weird feelings if he’s okay with me. Well I don’t know but I’m a bit confused.

PS: He doesn’t actually sound weird cuz we’ve been talking this morning but I feel he still thinks bout it.