Can any doctors or health practitioner out there help me? what do you think is my condition?

Now this is what happened to me.. yesterday, I think i drank something dirty when i bought drinking water from a sidewalk vendor.. After 4 or 5 hours, i started experiencing stomach pains.. a short time afterwards, I started vomiting.. then after a short time, I also started passing out watery stool (pure liquid with no formed feces) .. hmm.. diarrhea perhaps?

The pain went on for hours and i vomited about 5 times.. my vomit was clear fluids with a brown tinge, no food included, and had an extremely bitter taste.. and after a few more hours, i vomited for one last time and it was black in color..

until now, i am still not feeling well.. although the abdominal pain is not that severe anymore, but still occurs every now and then.. i have not yet started vomiting again since that last vomit, but my diarrhea still persists..

I have tried going to the hospital to have a check up.. but they didnt seem to notice anything wrong with me, except that I had cough and colds and some fever.. so their diagnosis was acute nasopharyngitis.. I wondered why they ordered urinalysis and blood exam only, because I was expecting fecalysis or something, since my main complaint was a gastrointestinal problem..

my urinalysis was normal, and according to my blood exam, my WBC and segmenters were both a little high.. they said this showed some signs of infections but told me that it was probably because of my acute nasopharyngitis..

they prescribed co-amoxiclav 3X a day for 7days, Nasatapp capsule 2X a day for 5 days, and paracetamol if ever i still had fever..

what do you think? I'm still a little skeptical about their diagnosis, because I'm pretty sure there's something wrong with my stomach..

Is it really possible that these symptoms are due to my cough and colds? i had cough and colds for three days already, but these symptoms never occurred.. is it possible that these was because i sometimes swallow my phlegm & nasal secretions when i am not able to expel them? sometimes there are streaks of sputum in my vomit, but can they really cause these symptoms?

I really hope someone can help me with this situation.. any opinion would be greatly appreciated.. thanks a lot!