MY MALE 2year old PITBULL is sick!?

I have noticed that my pitbull hasnt been acting himself lately. He is still a tad bit playful...occasionally drinks water and hasnt eaten all of his food but out of 100% is only eating about 20-30% of his food. just now he threw up. In his vomit there was 2 strings of gr and i guess a bit of his left over food. Overall his vomit was white. Seconds after he threw up he started trembling. Yesterday he threw up about 4 times when i took him outside he ran played just had a little bit of dark diarhhea. I called my vet but her office is closed. Any thoughts on what is going on with my baby?