Truth About Deception

I've been snooping on my boyfriend! We've been dating for almost a year. I feel terrible about it but I don't trust him. Earlier this year I found out that he picked up another woman while he was out of town. I discovered this by reading text messages from a strange number. He continued to contact her for months after their encounter. I never confronted him about it. He has also been in contact with his ex. His messages with her are way more elaborate and interesting than the ones I share with him, they have inside jokes, talk about their other friends, kid around with each other, and this goes on often. From first thing in the morning sometimes to late at night, while meanwhile I am hearing nothing from him. He claims they are just friends. But they obviously still love the attention from each other and it's almost like they're addicted to each other. They also see each other often, but he hides it from me or lies about it to me. What am I still doing with this guy???! Where has my self respect gone?