Ordinary day symptoms and conditions

I have taken 3 doses of an 8 dose course of doxy for a sinus infection. in the past i've been prescribed amoxicillin and had a little bit of dizziness on the first day but nothing severe. So when I took my first dose of doxy and felt a bit dizzy and woozy I figured it was nothing out of the ordinary. Day 2 however this got much worse with nausea and sweats and I spent most of last night trying not to throw up. This morning I woke up with no nausea and was thinking, today will be fine, the worst part is over. I wasn't due to take another dose until 6pm but at around 3pm I ate a bagel and before I had even finished it my stomach was turning over and over. That was 3 hours ago. My head is spinning, my stomach is still upset and I'm having cramps now. I've also started needing to pee like a racehorse. Suffice to say, there is no freakin way I'm taking another one of those things. I'm baffled as to why my doctor even prescribed it in the first place. I'm working on my masters right now and have an assignment due in 4 days so i have no choice but to stop the course and hope my sinus infections goes away itself. There are studies to suggest this drug is 3 times more likely to cause stomach upset than other antibiotics. Why do doctors not seem aware of this?