I've had a fibroid that comes & goes. It's definitely hormone related. It has never affected my riding, though. Sometimes I ride stronger during my period because I have extra stress to off load. How big is your fibroid? Mine can get golf ball sized (and I'm a pretty small woman.)

I second the complete physical recommendation. Also, look at your diet. Are you doing low carb? That can zap energy.

The problem with progesterone creams is that some are not readily absorbed. If you can get a doc to prescribe something from a compounding pharmacy, you'll know how much you're getting. Warning - a side effect of progesterone is lethargy. If you're very sensitive to progesterone (as I am), you really need to be monitored. I am 50 and I take a troche (under the tongue pill that melts) of estrogen, tiny bit of progesterone and testosterone. You said you're 40 & far away from menopause but your hormones might be changing slightly. The problem is - our hormones constantly fluctuate. So, even though we might be having hot flashes, night sweats & an uncontrollable urge to rip faces off, our blood tests could show that we're "just fine."

Could you be overtrained? All of our overtraining thresholds are different. If your diet hasn't been optimum & you've been under stress, overtraining could happen more quickly.

Just my $.03 (inflation, you know.)