Should I give up

My boyfriend and I have been at odds for a little over a week, all since I asked why he still kept in contact with his ex. I wasn’t asking or accusing him of trying to bring with her again but that same night we almost broke it off. Idk know what to do he’s my best friend. The person I wanna spend my life with. But since then our relationship isn’t the same. I don’t know what to think or how to act. We still say I love you and hang out but it’s just so different. Was I wrong to ask him? Am I fighting for a relationship that’s already lost?