Campus doctor said I was at low risk for HIV. Said I was unlikely to contract it sexually, it was more likely to get it from shared needles. True?

It depends.. The accuracy of those statements depends on the context of your conversation with the doctor. Anytime you exchange body fluids (blood, urine, saliva, seminal fluid etc) with an infected individual, whether via a needle or sexual intercourse, you are at risk of getting HIV as well as other blood borne viral infections like hepatitis B.