My twins are 13 months and there is DEFINITELY life after pregnancy. Once the babies arrive, your pregancy will seem like a distant memory. Mine does, anyway. I had a really rough pregnancy from the beginning. I was absolutely enormous during the latter half of my pregnancy (I only made it through 33 weeks). I can't imagine how big and miserable I would have gotten if I got closer to full-term.
I agree with Karen on the water thing. I took water aerobics when I was pregnant. Water was the only place I felt remotely comfortable. We also had a pool in our apt. complex and I spent a lot of time in that (I was pregnant during the summer).
Someone once told me that the reason you have trouble sleeping toward the end is nature's way of preparing you for sleepless nights when the babies come. I found that to be pretty accurate and it did kind of help me get prepared.
Hang in there, mama. Do you have the book "Mothering Multiples" by Karen Gromada? It's a good book to read now (before the babies arrive). Also, you might want to check out your local mothers of twins/multiples club in your area, if there is one. Mine has a buddy program for pregnant mamas. I learned a lot from women who had btdt.
Enjoy this time. It goes by really fast in hindsight. Having twins is the most amazing experience. I feel really lucky to have mine, even though I thought they were going to either kill me or drive me insane the first 6 months or so after they were born.