Wow - I cannot believe what i am reading. I am taking Periostat ...

Wow - I cannot believe what i am reading. I am taking Periostat (2 pills daily each containing 23.08mg Doxycycline hyclate equivalent to 20mg doxycycline) for my teeth and have noticed that at the same time, my adult acne cleared also. However I have felt the following: sudden weakness, light-headedness, nausea, indegestion, shaky hands, stomach cramps, pains in my lower leg, numbness in my right arm from shoulder to hand, itchy eyes, slight pressure behind my eye and even a severe itchy bottom yesterday. Also, I have recently felt like there is something inside my vagina especially when I sit down but I think this couldn't possibly be related could it? There are probably more things but not all at the same time. This has been over a period of three months and I thought I was being a hypochondriac. Could the pills really cause all this?