I don't have any experience homeschooling while pregnant with twins, so I don't have any advice about that, but I did have twins when my oldest was only 14 months, and I felt like you, could barely move toward the end. I basically survived on the help and charity of others (my mom and DH mostly) for the last month of the pregnancy.
FWIW, I also nursed my twins for the first year, so that is totally do-able, and I second the advice about the twin nursing pillow, that thing was a life-saver. It would have been much harder if I hadn't been able to tandem nurse, and the pillow definitely made that aspect easier.
You are only 3 days away from the point at which I delivered my twins, so here's hoping you have two healthy happy babies soon. And here are a few hugs for you...:grouphug: