I think your boyfriend feels offended because in his perception, you don't trust him and think he's going to hurt you.

Can you explain to him what's going on?
"I do trust you; else I wouldn't spend time with you, let alone dare to bevalone with you. I value our relationship enough that rather than run when you scare me by touching me, I try to talk it out so we can still spend time together.
But when I feel touch, my mind just goes back to all the times that, in the past, touch meant pain. I'll get scared and only after I realize that I am not in danger; that you are safe and will not hurt me. Only it does take me some time to calm down - when someone feels they are in danger, the body will release all kinds of hormones and stuff, and my heart will start racing: therefore I can't immediately be alright and feel safe again just because I realize it's you and not someone who means ill. This is why being touched, even by you, is very upsetting to me.
Please give me time. And know it has nothing to do with you."

Something like that? Explain why you get afraid (touch reminds you of x), stay afraid even when you realize it's him (body releases hormones, they have to get out of your system - can't just 'turn them off'), and that you do trust him and value your relationship.