any 1 know manga that have boring sex or present boring sex as a problem??

Ikenai Otoko - the main character is told by his boyfriend that he is bad at sex, so he tries to fix his problem by going to an AV production company. Very funny. That's all I know of.

The premise of the first chapter of Hidoi Otoko (AOI Akira) basically covers the "boring sex" part of the request. The rest of it is pretty good too even when it moves beyond that, so it's definitely worth a read.