I know sex isn't much of a big thing but if his thing isn't satisfying your thing then something's wrong. I don't know exactly what is wrong because there are numerous problems when sex is an issue so I don't know if its like him or just something he's doing but maybe you should bring other things like toys or try to help yourself ease into it mentally. Longer foreplay would help. Don't give up on that him completely.
And to answer your question, yes. If I wasn't doing a good job satisfying my partner I would be crushed if they left or was unfaithful to me