Your husband's attitude really ticks me off! Sorry. Can't help it. He's the one who needs to grow up, not you! He took the more insignificant part of the conversation (not that sex isn't important, it is!) and turned it into a major deal and made it your fault! Not to mention that he had a totally weak argument! He's with-holding(sp?) sex now as a punisment to you! And men say only women do that!
Yes, divorce sucks, but who is he to say that you'd have men in and out of your son's life?? I didn't meet my step-sons until my DH and I knew we had something good. It wasn't a casual thing, so it's not always that way! I don't have a whole lot of advice, but I hate to see you being treated this way and I think your feeling are justified.
Hang in there, and let us know how it's going!