Hi UCBear. Your question is understandable. I have been in a similar situation a couple of times. Both were because of different reasons. Since your boyfriend told you that you ask for it to much and that turns him off I would listen to him. If he is a good guy and nice to you in every other way then he is probably being truthful.
I understand how this change in your relationship can be frustrating, but the more you let it bother you the more he can see that. Your behavior, mad or sad, like that is just the same as asking him for sex all the time, do not let him see this attitude or behavior. So try to work on your relationship in other ways, focus on quality time, being sweet and getting along with him, without the mention of sex
If you usually cuddle at night I would do that too, but do not make any moves towards anything else.
I would try this for a while and see what happens. Be patient, give him more then a day or two LOL.
If this does not work then I say there is more to it then what he told you!
But give it a chance!
Good Luck