this may be total misinformation (not a doctor, not a scientist!), but, if you feel better once you get your bleed, that might be due to a drop in progesterone?? i think, in a natural cycle, it's this drop that initiates the bleed
i was diagnosed with PMDD when i had periods and felt horrendous the week building up to bleed- so for me it was a sensitivity to increasing proesterone during trhe week before bleedng, resolved by the bleed itself (and therefore the decrease in prog)
i did try a chemical menopause which removed all sex hormones but ynfortunately didnt work for me as also very sesitive to low oestrogen
sorry- not much help, but just wanted you to know that you're not alone and f course it's not an issue for me now i'm menopausal and without periods!!
sending posiive vibes, hang on in there
oh and agree with tinkerbell re exercise- i wish i'd done it!! i think i'dhave had a much better experience- am tryingnow but hard work now menopausal. i know you said your back bad- so i hope it gets btter soon and you can do something it's my biggest regret- not exercising and not eating healthily- i'veeaten utter crap the last couple decades!!- but am addressing it now, there's still time!! xx