Hi, For 2 Months Now, I Have Had Diarrhea, A

Hi, for 2 months now, I have had diarrhea, a fever, and vomiting daily. It started around the time my cellulitis disease acted up. Dermatologist put me on Bactrian and drained and cleaned one of the the sores. Saw my regular doctor 2weeks ago and he put me on a Z-pack, thinking maybe I had a virus. Thursday, I saw my dermatologist, again, who gave me an infinite supply of doxycycline, so I can regulate it myself. I am still with the same symptoms, but getting worse, in that my stomach is killing me, I am constantly burping, and now vomiting foam. Also, oddly enough, I have not lost any weight because of this. Please give me your opinion on what this could be. It's been so bad the last 3 days, I've been thinking about going to emergency room.