When my roommate has a guy over, i freak out, even thought they're downstairs, if i can hear them kissing or even talking, i'm anxious. what can i do?

Avoid or overcome it: There are two things you can do in general: avoid the stress (eg, leave when your roommate has a guy over), or learn to overcome it with therapy or self-help. It sounds as though you don't know why this makes you anxious; seeing a counselor or therapist might clarify it for you. Maybe guys/romance make you nervous? Stress management (mindfulness, imagery, deep breathing, etc) could help too.