Bad reactions to antibiotics...

Last Monday, I saw a new dermitologist for the first time. I used to go every month, to a different doctor (same office), when I had very bad acne (I took accutane two years ago for it, and it cleared up). The new doctor did not read my chart entirely, and prescribed me a tetracycline-derived antibiotic. I have bad reactions (nausea, headaches) to tetracycline, and so I had those symptoms after taking the new medicine. I only took it once, and informed the doctor about the side affects. She told me to take it again, which I did, last Thursday. Now, it's Monday, I haven't taken a pill since Thursday night, and I still feel sick. Could the antibiotic still be in my system?

Thanks! ♥ Chelsea