Trust issues?

Hey,So about six months ago I began spending more time with one of my friends at uni, and we started making out a couple of times. He seemed to be quite 'in to' me, and asked me on a proper date.On the date, he proceeded to ask that we went back to just being friends. I was quite hurt that he'd messed me around like this, and made my feelings known.Since then, we've been talking now and again- and he has now said that he has feelings for me. Apparently he finds it difficult to trust girls because of an ex who treated him badly, and that's why he freaked out before.So how do I help him to trust me? I don't know how 'full-on' to be... I'm quite an intense person. He definitely wants to give it a go with me, and I want to try and prevent a repeat of the last time.We won't see each other till I'm back at uni in a few weeks, so we're just messaging till then anyway. Any advice appreciated x