I was prescribed 100mg of Doxycycline Hyclate for acne cyst about 3 weeks ago. After 2 weeks of taking the med I developed a rash from my neck down. I was told to stop taking the med for a week to see if I was allergic to it....3 days later I had severe headaches, nausea and diarrhea. I feel depressed and flat. It's been a week off and no good news. This stuff is the worst med I've ever been on. Will these side effects ever go away?