
Speak for yourself. I've been with my man 8 years and I haven't so much as flirted with another dude. I've never cheated on any of my boyfriends and I never will. I have self control and as long as I'm with someone, I will stay loyal to them. Loyalty is very important to me and it really shows what kind of person you are to stay loyal to someone you love.
As for your friend, you should tell him that he's wrong for doing what he's doing and that he should get tested. If it were me, I'd want someone to tell me before I get an STD or HIV. Ask yourself what you would want if you were in that situation. It's such a bad position to be in, but you could potentially be saving a life. Try to convince your friend to come clean himself so u don't have to do it.