Thanks for your query at HCM
Firstly you need to relax before you jump to conclusions.
There are various causes of rashes infective as well as non-infective. It can be measles, typhus, relapsing fever, dengue, etc.
Diarrhea could be also due to
Enteric fever, colitis, drug induced. Get Full blood count, including
platelet count, and examination of a thin film for cell morphology,Urine microscopy and culture, Serum chemistry,
Blood culture. It you have pustular lesion you can get culture/sensitivity performed especially for streptococcal infections. You can also get HIV Elisa test repeated. You need to start an emperical antibiotic treatment first. As you could also be suffering from intestinal TB as symptoms suggest you can undertake
ultrasound /ileo-caecal junction biopsy test for TB-PCR. Set of other investigation may also be required.