Very few people are injection drug users, while the vast majority of people engage in heterosexual sex. You can't compare rates by looking at total case numbers, which still nevertheless show more people in America getting it from drug use then heterosexual sex, overall.
I think I once read that white heterosexual males, who don't use drugs, have a better chance of developing breast cancer than getting AIDS.
Taking a quick look at the numbers. About 1000 white men get breast cancer each year and less than a thousand get HIV through heterosexual sex. The bottom line is you should be more worried about your titties Willco than getting AIDS.