What are signs of infidelity?

becoming withdrawn from your partner or overly loving, hiding things, constantly having your mobile hidden, changing all passwords on computer that the partner knows, body language, if you ask your partner about it and they become silent or cross their arms or seem distant thats also a good way of finding out. I have been cheated on in the past but I was in an abusive relationship so just took it as I was too scared to leave, I have also cheated on somebody and I believe this is because the way i was treated. Has anybody cheated because they have had it dsone to them, does it mess up your relationships? I am currently in a relationship and we met through me cheating on my ex with him he knows all about my past and is very careful about some of the things he does as i am still quite paranoid of getting cheated on again, although I know he wouldnt do it to me its always in my mind