Why does my man lie to me

Hello my boyfriend and I have been together for almost 3 years. He has lied to me a lot and every time he gets my trust back, I find out another lie, or I see messages that he has sent to other women he went on his my space. He didn't know that I was looking, and he had a messages on his my space talking to one of his friends about another women, saying that she can be with him, and the date, on the messages. Was 2 day before our one year of being together, and how hot she is.

It crushed me and I have seen one on his phone talking about another woman's breast job that she had done, asking her if she plays with them, and telling her they look nice. My body isn't good looking at all. I have flab and stretch marks from having 3 kids. When we are in bed doing adult things he closes his eyes, or he don't look at me, and every time I say something about it, he always tells me that I wont let him look at me, but I do. And when I say something bad about the way I look, he tells me I'm hot, and there isn't nothing wrong with me. But he thinks that Jessica Alba is the hottest. But when I ask him he always tells me no, and that he was just picking.

So I have been talking to him about me having surgery on my problem areas, but he always says no, you are fine the way you are. If he thinks that then why don't he tell me without me having to talk about myself. And about a year ago his ex brought there kids to the house. He wanted me to leave, but I didn't. I just stayed in the room. He told me that she would be leaving, but she ended up staying the night. Yes, I can understand that. She had a little baby with her, but its her fault for her driving all day. He said that he let her stay because of the baby.

I just don't know what to do. What I think I should do is just not say nothing about the way I look, and one day get new clothes and dress sexy and see if he says anything. I don't know, someone please help me.