How often does this happen? Has it been every month for a period of time ie 2 years or is this a recent phenomenon following on from your depression?
Very good news that you are going to see a psychiatrist soon. Only they can give you a diagnosis of bipolar or anything else ofc and a GP shouldn't be doing that. That they have referred you on is great. Please be sure to mention any out of the ordinary behaviour, including these periods of increased sex drive.
Hypersexuality is a main symptom of a manic phase in bipolar, along with excessive spending and feelings of invincibility etc. There are, however, other things that could be causing this. I know it's tough but now you have your referral try to not self diagnose :) it's entirely possible it's something else too.
And yes to getting your thyroid tested. If it is fluctuating that much it is worth keeping an eye out it. GPs I found tried to brush me off so you may need to nag.
I think if you are worried have an open discussion with your partner about it. I had to with my dh and he was actually very supportive and we found ways around it which were mutually beneficial :) it sounds like you have a strong relationship. It isn't normal behaviour so if you couch the discussion in medical terms and that you need to explore it with your psychiatrist I am sure he will help you. Again, not saying you have bipolar as this could just as easily be a hormonal imbalance, but there is information available on the Bipolar UK website that may help.
Coping mechanisms in the meantime - as a pp said, masturbation or asking do if he's up to it a bit more often at those times.
Good luck 