Maybe a support group with similar circumstances exists in your area. You can contact a local therapist who knows about group therapy and find one that way. The on and off again - did he date others when you guys were "off" or did the "off" happen when he dated (ie. cheated?)

In terms of trust of someone who has cheated, I can relate. I was one of those who has cheated on both my gf's when I was young and also on my marriage. Younger, I just wanted to get to know people. Not being married, I was interested in meeting new friends/girlfriends/dating. A lot of times a gf/bf couple "act" married. One gets upset when the other even talks to someone of the opposite sex rather than dates them. This lack of trust is really self-directed. You may be seeing yourself "losing something you cannot hold onto" rather than trusting yourself that you know he'll come back. Fighting the trust tends to come out in hurtful attacks such as "where were you??" "who were you with?" "did you talk to her?" - that kind of thing. Guys really are put-off by this - they start to feel like "huh, maybe if she wasn't so naggy, I could handle this well. right now, I don't even want to be around her until she stops that." As a guy, I have a "trigger" and that's questions. Not "how was your day?" questions - but "why didn't you come home at 5pm like you said you would?" Challenging questions like that are really a cry out for soothing of trust issues. There are times when I'm a lamb and still feel accused of doing something wrong, so it can feel bad on his side too when you get jealous.

I think we're all taught "don't trust him - he'll just leave you". This truly isn't the case. A guy wants to know he's loved for him - not for whether or not he does what he's supposed to do. "I'm unique - love me for it" is what a guy is thinking. If a spouse starts to throw darts at that and challenge him, he will stray and eventually leave.

I think trust issues and jealousy is fixable - but the real issue is finding out where they came from. usually, it's parents teaching their kids to be that way, you learn it from how mom and dad act to each other. Then, when you can "use those skills" in real life, you start to mimic what's been taught. By working with a therapist or in group counseling - it is possible to slowly and healthfully remove those traits and be more trusting. However trust is not the same as being walked all over. You still need boundaries and decent ground rules between two people in a couple.