Help With A Tropical Stomach Bug From Indonesia.?

I went on an adventure holiday very recently to the islands of Java and Bali in Indonesia which involved many long days out in the hot sun and temperatures over 30 degrees. About half way through the holiday I became very sick with a raging fever that came on suddenly in the middle of the night. I would feel boiling hot one moment and freezing cold, shivery and weak the next. Over the course of the next few days I developed terrible stomach cramps that meant I could not even get out of bed as well as a persistent feeling of nausea and the inability to keep any food, tablets or liquid down for longer than half an hour. The problems seemed to last for three days and then eased on the fourth and so I was able to continue with my holiday with only mild discomfort. The stomach cramps were still present though and occurred every time I ate anything more than a small bowl of soup. Now, ten days after my ‘recovery’ and two days after returning home my symptoms have suddenly reappeared in much the same way that they did in Indonesia – raging fever followed by stomach pain and nausea. I have a doctors appointment for tomorrow morning but I am very worried that this may be something more than a simple stomach upset due to the sudden recurrence. I would be very grateful if anyone could shed some light on what this could be, or recommend anything that they think would be good for me to eat/drink in this situation as I have not eaten properly for days and find it very difficult to keep anything down for long.
Just some background information – I have no previously-diagnosed medical conditions and I have been taking the malaria tablets prescribed for me by my doctor (Chloroquinine and Proguanil) and have not missed a dose. I have taken both of these malaria tablets before with no bad reaction and so I am doubtful that it is the malaria tablets causing my problems.
Any help would be MUCH appreciated.
Jana