Yes, this sounds normal. Taking the hormone therapy as you are taking it, 10 days/month, may keep you bleeding. If you had gone 15 months without a period, your body is probably pretty close to quitting. You might stop the cycling by taking the Prometrium everyday. This is perfectly safe. If you continue to breakthrough and bleed or have spotting, it's a good indication that your body is not ready to stop. I also like the continuous dosing because progesterone is very helpful with sleep and mood issues, so the more you are on it through the month, the more help you'll get with those symptoms.
Good luck,
Sandy