Dreams!

I'm happily married and really love my husband I wouldn't dream of being unfaithful to him, but the last couple of months I've been having dreams about having sexual relations with other men and forgetting I'm married in my dreams I've had it 4-5 times now and it's not very nice I haven't told him about these dreams because I don't want to upset him, is it because I'm pregnant I'm having strange dreams or any other reason?