When ur girl/boy start to think her/his Ex, What's in ur head ???

It would worry me, and if I felt able to, I'd ask my boyfriend if he felt able to talk about his ex with me and perhaps we could share his feelings about her and try to come to some sort of compromise, but within that talk I'd want to establish if he were still in love with her. If so, I'd ask him if he wanted to be with me or her. If he said her, then we'd have to talk about whether that would be possible or not, as she might not want to be with him any more. No doubt we'd then conclude that I was second best, then I'd have to go away and think about whether I'd be happy with that or not. If not, then we'd probably have to split up while he goes off and does whatever has to be done in order to get over his ex. If we ever got back together, I'd have to make sure he were completely over her before we got into anything serious.