I was taking doxycycline for acne and i have been taking it for about two months now. I started to feel nauseaous all the time and on some occasions, i threw up for no reason and without having any food in my stomach! This made my life crazy! I was irritable alot and always feeling sick! I now have to have a biopsy- a tube into my stomach- to find out what is wrong with my stomach. I might have an ulcer. Doxycycline is the reason for this!