It sounds like high estrogen. You may have a low ovarian reserve and your body is trying really hard to ovulate but it’s not happening. So high FSH stimulates the ovaries but if they aren’t responding, estrogen can rise in response. If/when you don’t ovulate, there’s no progesterone to stabilize the lining, and no period. Eventually, the lining can build up to a point that you spontaneously have a period; it’s an anovulatory cycle. Maybe that’s what happened with your 8-day bleed. Then with things somewhat reset, your body tries again to ovulate, even harder. Sore boobs, nausea, that’s high estrogen.
You might be well served with the progesterone side of HRT if you are having enough estrogen right now. Like a Mirena. You could also get estrogel if you find you need that as well, but it sounds like you won’t want much.