I don't think that jealous people usually change. I like it when a guy it protective of me and care what happens to me, but not when they're jealous/paranoid/accusatory.
I just got out of a 2 year relationship that was like this. I was 200% loyal. I gave him and "us" everything I had. He would have such a fit if I had a couple of drinks with coworkers after work, went to dinner with my sister, or just about anything I tried to do without him. If I went out, it wasn't even fun because I'd come home to him accusing me of doing things that I would NEVER do. I hate to even admit this, but I went out with my friends (without him) maybe 5 times in 2 years...it wasn't worth the ugliness when I got hom.
It got really out of hand when I started working out a lot-- and started working with my trainer. He seemed to think that me going to work out sounded like I was saying I was going out to whore my body on a corner. It wasn't worth the fighting. It was really hard, but I chose to leave.
Ultimately, people who are jealous like that are incescure about themselves and just project that negativity onto their partner. I suppose they're only justified if their partner has a history of cheating...in which case, they knew what they were getting into. Do what's best for you but know you can't change another person.