Whatever you do, he doesn't believe in your love and the reason why he's still with you is that he trusts nobody and that fortunately you're probably the person he trusts most.

I care more about your feeling and about your not being hurt in the future.

If he doesn't believe in your love, he should explain in more than a simple phrase "gut feeling" and it's called communication.

You should not be suggestible and should be yourself. You should not try to convince him if you don't know what he doesn't believe. If the problem is his, your changing yourself doesn't help.

In such a relationship, both suffer, but he suffers whomever he's with, unless he doesn't care about his girlfriend; while it's your choice whether to keep suffering.

It seems you get hurt when he doesn't trust you and you have been hurt for 2 years; even if some day you don't need to be hurt anymore, whenever anything reminds you of his distrust, the hurtful feeling will come again.

The point is not to stay or leave, but that you should not be suggestible and should not humor him, losing yourself.