Panic attacks- trigger warning: rape, abuse

I was super nervous to have sex with my boyfriend now since I had technically never truly given myself to someone. He is very respectful and asked me at least 4 times before we actually did it, to make sure it was okay. And it was amazing! I have never experienced someone loving me like that. 

Anyways, we were getting into it and I was enjoying myself when all of the sudden I went into full blown panic attack. He was so sweet and helpful despite the situation. We have had sex again a few times but even if I don't panic during, I will have nightmares that end in me waking to a panic attack. I know it's something I have to deal with but I feel horrible for him. I love him so much and I wish I could be better for him. 

Any suggestions on how I could deal with this?