I've heard of problems like this before where men can sense your low self-esteem, and it makes them less likely to want to be intimate. Guys feel better about being intimate with their partners when their partner feels good about themselves. Have you tried other ways to attempt to be intimate with him? Such as wearing lingerie or a lot of foreplay? Maybe you could ask him while you are being intimate to satisfy you. Do you hug/kiss outside of the bedroom? Is there any type of physical contact besides being intimate? If not, there might be other problems that lie deeper than just intimacy and self-esteem. I hope this helps!