Have enough self respect to make guys wear a condom every time you have sex. I see so many posts from people freaking out that they might be pregnant or might have a disease after unprotected sex, but it is so easy to prevent pregnancy and STIs. If you're too embarrassed to buy condoms, you shouldn't be having sex. If you can't afford them, planned parenthood, county health departments, school nurses, college health centers, etc will give them to you for free.