Please help me b4 i destroy a wonderful relationship?

I fell in love with a stupid boy when I was 20 and i thought life was perfect and he my my first everything. in addition to that i am so cynical and don't trust much. I gave him my heart and in the end it got broke. I've been with the most amazing man in the world for a while now and things really are great. We had our first real fight a couple weeks ago and after w talked about it things were totally fine. Suddenly all these insecurities from the past come to the surface and even though i know he isn't the type to walk out i still project this crap onto my new relationship! It's driving me crazy, how can I change this!?! i don't wanna mess this relationship up! Please help!