First Time Doing Oral??

Long story short, my boyfriend really wants to go down on me. I've given multiple people head before, but I've never had anyone go down on me because of several insecurities (I'm a sexual abuse survivor, self conscious about my labia, I don't want it to be gross, I'm worried about getting a UTI, etc etc.) Anyways, I could never see myself letting anyone do anything sexual to me before I met him, and like, I actually do want to have him go down on me. So, how do I know I don't smell gross? 😂 and do you guys have any tips or tricks for the occasion? Advice would be greatly appreciated, thanks!!!