My boyfriend has NO sex drive!! help?

hi, iv been with my boyfriend for nearly 3 years and we are like best friends and i love being with him but the only problem in our relationship is he has NO sex drive, his penis has a totally different brain because he goes hard but then when were having sex we could switch positions and he will go floppy suddenly and wont go back up no matter what i try to do. i really need help because were having sex like twice a month because it seems more hassle then its worth!! HELP!!!