Am I ruining my own relationship?

My relationship with my boyfriend of 11 months has been great until now. I am 31 with one child and I have been through a string of bad relationships. Well this man helps me with my bills, groceries, car repairs, takes me out and spends time with me. Well ever since he went out of town to see his kids I have been a wreck. I thought he was cheating, but I knew I was being insecure and kept my mouth shut. Now since he has gotten back I have lost all confidence in the relationship. For instance, last Friday night he called and said that he was going to get a bite to eat and that when he got home he had things to do and would call me in the morning. I thought this was strange and became upset. We always say goodnight. I couldn't sleep and called him at 5:30am just to see if he would answer and he did. Well I was appeased for the time being but I had a bad attitude all weekend. Yesterday I decided to check his email-yes the invasion of privacy and I saw that he recently signed up for Match.com(2 days ago. I addressed my feelings with him(not divulging the invasion) and all he says is that he is happy with me and needs me to be confident and secure in our relationship. That he does love me and he continued to ask me what he can do to make me feel more secure. Am I destroying the happiness I once had?