Is gas a symptom of early hiv? if i'm experiencing it 2 weeks after possible exposure?

Probably not HIV: Intestinal gas (belching, farting, intestinal rumbling) has many causes -- infections, diet, and others -- but HIV isn't among them. Also, at age 18 the chance of a new HIV infection probably is low. Regardless of symptoms, if you think you are at risk for HIV (unprotected sex, multiple partners, shared injection equipment, etc) see a doctor or clinic to evaluate risk and check for HIV and STDs.