Wellbridge is expensive, but they have the advantage of no contract. So it may be worth it for this situation since it is temporary. They do have a student discount, too.

They doubled their floor space over the Winter and added new equipment. My experience with the pool, however, is that it is always booked with classes or family time. There is only one lane dedicated to laps and I've never used it in my 9 months of being a member.

If you have a car, or are okay with a long subway ride, the Boston Sports Club at Wellington Station is the best gym I've ever seen and has a huge and awesome pool.