My boyfriend wants to give me oral but...

I'm really nervous. Today we were making out and grinding on each other. He has also fingered me and I've given him handjobs and blowjobs before, but when he asked me if I wanted oral I simply said "only if you want to" and of course he wanted to but when right before he was about to take my pants off I just couldn't. Idk I told him that I was nervous and he said it was okay and that we don't have to do anything that I don't want to and we went back to what we were doing. On the second makeout session today he then offered if I wanted to try to 69. I was like yea but the same thing happened again 😩 I'm just so nervous about doing him doing it and I know he wants to please me but I feel like it won't be enjoyable for him or if he sees my razor burn he might think I have an STI. I know it's silly, but these are things I actually think about which causes me to back out like last minute. We are both virgins btw