Best of luck, hun! Even if you don't pass this next test you've got lots of time. The only thing I found about pregnancy and driving was that as I got bigger, I found the belt across my lap became more uncomfortable and I was shifting it all the time as I drove. Not great. I passed second time at the ripe old age of 28 a few years ago. If, like my instructor, your instructor insists on a lesson before the test, maybe tell him/her that you'd rather not have it, or just a short drive before so that you're not overtired.
FX for 17th xx