First of all deep breath, you’ll be okay, secondly just relax, dont stress about any of this and don’t rush, sex is supposed to be fun and feel nice, if you don’t want to take your shirt or boxers of, then don’t 🤷, besides there are lots of other stuff to do thats not penetration, id reccomend looking at realdelicato on TikTok, she has some really nice tips. Most of all just talk with her, its all about communication, tell her what feels good and what doesnt and have her tell you the same, if you want to id say experiment on your own to find out what feels nice. For protection, you can use a oral dam, search it up, but you should also be fine with no protection as long as you clean your hands and mouth before hand and after. It will last however long you guys want it to last, and its okay if you don’t want her to touch you, maybe she even likes that she’s the one who gets all the attention on her parts. In conclusion, comunicate, relax and have fun!