Excessive menstrual bleeding symptoms and conditions

Two years ago I received a shot of Kenalog in my shoulder (40 mg) to relieve calcified tendinitis. It worked wonderfully--all pain disappeared for more than a month (even my migraines). However, my period went berzerk: I bled for weeks on end. It finally stopped, then a week later it started again. I suspected the Kenalog was the cause since the period problems started at the same time as the injection, but 2 different doctors (family physician and gynecologist) both told me that "no way" could Kenalog cause excessive menstrual bleeding. My orthopedic doctor, who gave the injection, said "well, maybe." My periods went back to normal after a few months and I had no other side effects.
Now it's 2 years later and my shoulder was hurting a lot again, so I went for another Kenalog shot. I was hoping that it was just a fluke the first time. Also, this time I received much less: only 10 mg of Kenalog vs. 40 mg. last time. Well, the shot relieved about half of the pain, which was still enough to allow me to do physical therapy, which will provide a long-lasting solution to the pain. But once again my periods are all messed up! I have been bleeding for 6 weeks now, with no end in sight! I was prescribed progesterone (10 mg, once per day for 10 days) several days ago to stop the bleeding and re-set my cycle, but so far, the bleeding hasn't even slowed down. I take Tylenol and naproxen for the very painful cramps. This time my gynecologist DOES think the bleeding is from the Kenalog, but he is also checking out other possibilities. They did an ultrasound and found a small fibroid, but they don't think that's the cause. I have to go back in 6 weeks for a follow-up. No matter what, I will never take Kenalog again!!