NPP is built on a progestin backbone so to speak, and it can and does effect sex drive. I will assume you have heard of deca dik? that is common more so from nandrolone decanoate how ever many people get like effects from NPP. usually not as long lasting as you though. that said the first place I would try is two fold.
1st run inhibit-P from sns to lower progesterone.
2nd run Arimahex from Apex to normalize sex hormones.