I have to admit, i'm a bit worried about you, Sostenueto. You got up a 5 the other day to drive everyone around for hours. You need to be looking after yourself and letting others look after you, but you are putting everyone else first.
If you can't tell your DGD's mother until after the exams are over, because she'll not be able to hide it from your DGD, what about just confiding in someone else in your family and let them covertly help you? Even if its only having someone to talk to about it, I think that would help a lot. A problem shared is a problem halved, etc.