Worried about Fiance & other Man...?

Ok, so I am engaged to this guy, and am jealous of one of his male friends. His friend who is over 30years older than him texts my fiance pretty much all day occasionally hits on my fiance and i am jealous and worried. I have talked to my fiance about this and from what he said is that he only talks to him to make him feel better (his friend is very lonely and depressed) and that he feels weird when his friend hits on him also. Yet my fiance gets extremely irritated that i am jealous of his friend and that he keeps telling me he wont leave me and loves only me and i still get worried. I get very irritated that this guy is hitting on my fiance and texting and talking to him all day. I cant talk to my fiance about it, because he is apparently doing it to make his friend feel better. What do I do?????????