After all the questions your doctor asked and your replies, surely they recommended a
sleep study?
Sleep deprivation causes decreased libido and symptoms that look like depression, plus daytime sleepiness, fatigue, awaking unrefreshed. If you have some episodes that look like apnea that your boyfriend sees, there's likely many more he doesn't see, as he is either sleeping (or peeing). By the way, frequent nighttime urination can be a sign of sleep apnea. Maybe he needs checked too.