Fears in a relationship

As the relationship grows new things start to make their way into to your life. Sexual stuff as never been a taboo in my case but has proven to be something that gets me questioning a lot. 
Last time I try to please someone in that way was 3/4 years ago. Way younger, way too many hormones, way easier. 
Now is so more complicated. Or has been. 
I'm aware that self-control kicks in many occasions but what about the other times? Surroundings? Probably. But again that only explain part.
The person trying to please the other is a major factor. And that person was me. 
My knowledge for this type of stuff is almost zero when it comes to making him feel good yet so was his knowledge and daaammn if the boy can't make you happy easily. 
It's just me. Am I not good enough? Sexy enough? Sexual attractive enough? Yeah... Probably not enough. 
That's my fear. If this relationship is supposed to be a long term kind of thing then it will become a problem. 
Learning it's easy and fun. But will he think that teaching me, or whatever, will be fun and, well, worth it?