Hello and welcome to ‘Ask A Doctor’ service.
I have reviewed your query and here is my advice.
The most common cause of acute
stomach irritation,
diarrhea and loss of appetite is an acute infection of the gastrointestinal tract either viral or bacterial. These symptoms are not usually related to a sexually transmitted infection. Most sexually transmitted infections present with discharge, pain or discomfort on urination,
fever, change in the color or odor of urine,
rash. The discoloration on the tip would need to be monitored to see if it changes.
A rash can sometimes evolve from a discolored area to form blisters, in some cases. You should consider STI testing to make sure that you are okay though if protection was used, you should be fine physically.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. Michelle Gibson James