It's probable that you need to increase your Synthroid dose. Estrogen makes levothyroxine work worse so when on estrogen supplement you're more likely to get hypo symptoms ie. the levothyroxine dose needs to be increased (it's not just the numbers that get messed up
). And when you stop taking the pill you might need to decrease your dose (I had to decrease my levothyroxine dose by 37,5 mcgs when I went totally hyper a couple of months after stopping the pill - and still I felt and my thyroid levels were better than on the pill). Don't take your levothyroxine and the pill at the same time.