How to enjoy giving oral (and be good at it)?

I am struggling with giving my partner oral (BJ) both in terms of me actually enjoying giving and being confident in what I am doing. The thing is that I want to give him that pleasure, but my struggles are making me scared to even attempt it.

My first problem is taste and smell. This isn't a problem with his hygiene or anything, I am just very sensitive when it comes to genitalia taste/smell. I also don't like kissing him after he has given me oral for the same reason. Is this just something I have to deal with? We both shower every time before we get intimate and he washes himself well.

My second problem is that I am not very experienced and cannot keep going for long. His penis is quite girthy so I basically can barely fit the head in my mouth and my jaw gets exhausted and hurts pretty fast. I try to use a hand to stroke while I am at it, but I still feel like I don't really know what I am doing.

Giving oral is something really intimate and almost scary to me and I get in my own head a lot, but I would really like to give him a pleasurable experience. Any tips are welcome. Thank you!