Has this happened to anyone before? I take 10/500 every 4 to 6 hours for pain. I have severe migraines and endometriosis and chronic low back pain. I have never had this happen before, and it always works.At least most of the time it lessens the pain... i don't know if its me or the medicine is a bad batch. it looks the same and i get it from the same place every month. Any ideas?