Boring relationship?

Okay so my boyfriend and I are starting to get in this rut of being bored.. we've been together a year on Friday.. we love each other and definitely want to be each others forever.. but we are long distance and it's just kinda hard to keep it going and not start to get boring.. we were joking around a bit about having a threesome when he gets home and then it turned into talking about having a polygamous relationship? I don't know how I feel about it.. it sounds intriguing BUT I don't want to feel as though I'm cheating or using the other person.. Second of all.. If we were to have another person enter I feel as though I wouldn't want them anymore as soon as my boyfriend and I moved closer.. and third of all.. I don't want to share him so isn't it kind of selfish to make him share me? Ugh so many unanswered questions!!