Don't be embarrassed. Your questions are valuable no matter if you do have to take up a lot of space here.
There's that old saying "three's a crowd" and that sometimes causes problems no matter what age we are. The guy on the 3 of Pentacles in RWS decks is standing apart from the other two people. You and your boyfriend are the two people standing together while the other guy is further away. Your boyfriend's friend is an outside influence and even if he tries, he won't be able to come between you if your boyfriend really has a sincere love for you. The friend might try, but it won't work if you don't let it. I'd read this card as "keep your distance" from this guy. Let your boyfriend just maintain a friendship with him if he wants to, but don't make it an issue of you giving your boyfriend the ultimatum eventually that it's either you or the friend and your boyfriend has to make the choice which one to hang onto and which one to let go of.