Can my controlling husband change?

Hi, I'm a 39 year old woman, I have three kids, I've been married for 13 yrs. I've been unhappy in my marriage for 6-7 years, and though I've tried to leave I never had the courage to do it until November 2010. I asked my husband to leave (I can't believe he did) because of major problems we have. I'm not perfect, but it's very hard to deal with the stress of everyday when I feel like I have to walk on pins and needles at the house so that he won't get upset, start yelling, get grumpy, throw things, hit walls, belittle me..and all of this in front of the kids. A few weeks after he left I started wondering why he's so suspicious of me, he put a keylogger on my computer. Then it dawned on me that he may be cheating. I found out that he was cheating on me with an 18 year old, and I believe he's cheated a lot over the years. Now he says he loves me so much, that he literally can't live without me. He proposes all kinds of possible solutions, and it all sounds great! BUT we've been through this kind of thing so many times before. It's just a vicious cycle we go through. Problem is, with us, when it is good it is really so good. When it's bad it's really horrible. There's not much in between. I love him, but am afraid to believe it could work between us. In the last few weeks I feel I'm being sucked back in. I even had sex with him a few times (I'm so mad at myself for that). He wants to go on a "date" with me tonight, and believe me, I'm so tempted! Times can be great with him, but I know that this won't last. I guess my question is.... Can men like this change?