Thank you for all the supportive comments. It really helps. I did send an email to the doctor, but she has not responded.
Strangely, we had a really nice weekend. I just can't let myself believe that anything really bad is going on, so I'm in serious denial mode. We took all the boys to Petco, without a stroller, which was a first. My husband had B., who isn't interested in looking at all the animals, but does like to jog around the store. I had J. and G., both of whom are very interested in the fish and the birds, so we did well. I kept wondering how my husband was doing with B., and then I'd hear a loud "Zubadee, zubadoo!", which is one of the "jargon" phrases that B. likes to say when he's very happy.
This morning I took B. and J. to church with me. As J. later reported to me, "Him just cry a little". B. even sat at the table for snack, so the morning was a success. When I went out to the playground to pick the boys up, B. was up on the play structure, looking very pleased with himself. G. stayed home and napped, because he had woken up at five saying "Ah-doo! Ah-doo!", which means all done with sleeping, apparently.
I figure, if we are going to find out that the MRI doesn't show serious problems, then I won't need to have worried. And if there is a real problem, then it's good that we had a weekend together of enjoying ourselves before we start dealing with it.