I was prescribed doxycycline for bronchitis/pneumonia and an ear ...

I was prescribed doxycycline for bronchitis/pneumonia and an ear infection. I've been taking 100mg twice a day for four days now. The heartburn started last night, and though I've had mild cases before, this is unbearable. I cough and feel like I'm going to throw up. I drink water, I feel like I'm going to gag. I can stand, I can sit, I can lay down, doesn't matter... feels like I have a rock lodged at the back of my throat and my throat feels scratchy all the way to my sternum. The headaches come and go all day and I feel like I'm in a constant fog. I was told it was not an allergic reaction, but it is a "normal" reaction. I won't take this med again. It isn't worth it.