IMHO, when you're in love with someone, you're always a little bit insecure (whenever you're on to a really good thing, there's always that fear / worry that it may abruptly end)
Anxiety can be severe for some people and others not, no my ex boyfriend used to get anxious about little things which would build up to a big thing. Then I wouldn’t know what to do because he would find it hard to breathe and he just wanted me to sit there with him but not talk when it was happening. No comforting or anything. But he was the one that needed reassurance and had major insecurities when I went to parties etc, but he was the one that cheated on me. So if a guy/ consistently has anxiety about you’re relationship it’s most likely that he might be guilty of doing something to u, one of my friends had a similar experience too but her boyfriend was insecure not really anxious. As for a girl, I only get anxiety from exam results or things affecting my success, I can’t sleep, it makes me sick and my heart races and constant over thinking but it doesn’t affect my relationship that I am in now.
Woow ur ex needs reassurance and he is also cheating on you? Why is that? What happened may i know? And what do you mean when "he might be guilty in doing something to you"??