My doctor says I have Bronchitis and prescribed a 10 day supply of Doxycycline. I took my first dose this evening and have had a very upset stomach. I was wondering as I read the prescribed use that it is for bacterial infections and is used when penicillin is not effective. Why didn't my Doctor prescribe Amoxicillin as a first line of treatment ? I will add that I am leaving on an Eastern Caribbean cruise this Saturday...but I sure don't want to continue feeling like I am right now. Is there anything I can do to lessen the upset stomach ??