Stomachache for the past 2 weeks. ache started same day after protected sex. last week i was constipated with stomachache this week i have diarrhea with continued ache. could this be an std? maybe hiv? no health insurance wanted to try here first?

Your symptoms are highly unlikely to be due HIV and probably are not related to your sexual activity. For diarrhea you may take Imodium or PeptoBismol. If that does not resolve the issue in a couple of days, it would be prudent to see a doctor. Regarding your fear of HIV get a 4th gen combo test at 6-7 weeks after the episode of sex. For info: https://www.cdc.gov/std/default.htm