I want him but don't know if I can do this

I've had feelings for a friend for over a year, always kept it to myself because feelings are scary and I thought he was straight. Then he kissed me six months ago. It was amazing, first time I kissed a guy and it was beautiful. Nothing happened afterwards, we didn't talk about it, I thought it hadn't meant anything to him. Then four months later it happens again. We kiss, we make out, things get steamy. Then he tells me that he wants to f*** me. I immediately recoil, basically kicked him out. Took me until today to bring up the topic again. I messaged him, apologised. Explained that I got overwhelmed, that things is a difficult topic for me. Confessed that I'd never been intimate with a guy. He was very nice and understanding. We keep texting and I end up with my hand down my boxers. We end up sexting. I don't know what to do. I want hm so badly but I don't know if I can do this. I'm so fucking tired of being terrified.