Advice please!

Aggie
My BF and I have lived together for 4 years, we have a 3 year old son together and he is the best father I've ever seen. We've had our problems though and have spent time apart during the last four years due to trust issues. When I was pregnant with our son he rekindled a long distance relationship with an old flame in his hometown. I had my suspicions, especially when he asked if she could be our son's Godmother, claiming she was his best friend in the entire world and I had never even heard of this girl in the time we had been together. Of course both he and her lied to me when I confronted them, eventually I had proof of my suspicions and he came clean. About 6 months ago I decided that despite everything that happened, he had more than redeemed himself and that no matter how hard I tried to deny it I still am in love with him. So we are giving it another go and things are going well for the most part, but I have a tendency to run and distance myself when I feel like I'm getting too close to someone. Any advice on how to work out the kinks in the relationship without running away like I always do?