Boyfriend is getting a roommate?

We've been together 6 months. My boyfriend is 30 and a friend from work will be moving in soon because of a divorce. It's for 2-3 months, but who knows if it could be longer. I stay at my boyfriend's every weekend and I'm not happy about this at all! We've had this great relationship going - lazy weekends together, being able to be *ahem* as loud as we want, sharing a garage, cuddles in the kitchen. Now we're going to lose that. I'm also worried that his work friend is going to tell him that marriage is a bad idea and to dump me, or that he'll try to get my boyfriend to relive his single days with him. Am I overreacting? Tell me something so I can feel better and not get mad at my boyfriend...