is it wrong of me to have distrust in him? and ask him not to speak to someone?

my boyfriend and i have been dating for almost 3 years now, a couple weeks ago i found out that he cheated on me while i went out to dinner with some friends of mine, ititally he denied it untill i told him that i knew mostly every thing there was to know about what happened that night. one of the things that floors me the most is the fact that the dude came to him after it happened and told my boyfriend that he may have gonorrhea, and proceeded to tell my boyfriend that if they had it he should blame it on me, he also tried breaking us up by saying rude an obscure things about me. ive asked my boyfrined to stop talking to him but yet he still does and they still talk about meeting up again...