Bumbleclat, many
for your loss.
Feeling tired is absolutely normal as a part of grieving full stop, never mind the travelling, anxiety before your mother's death and your pregnancy. Two weeks is no time at all, in fact there is no "right" amount of time.
My DH died suddenly, though the hospital visiting was a short and intense few days as he was kept going for organ donation, so I can identify, though in only the smallest way, with the exhausting to-ing and fro-ing.
I find I now have a skin to few now, so the upside is not taking shit of any kind, and saying so. The downside is the shit might not be intentional on the part of the shitter. Only you will be able to tell how this is working for you. A wonderful book I read on grieving is that it doesn't make people change, just exacerbates inherent behaviours, so my skin too few is a concommitant of my day-to-day arse from hell-ness.
I suppose what I'm saying is to pay attention to yourself ( and your baby) 
I'm seven weeks down the line and, as a teacher too, feel the pinch of not feeling entirely well-planned as I would like. Fortunately, I'm in the far more forgiving educational world of Australia.
I'll be blunt here; if your school is averse to cutting you some slack having had your holiday consumed by death and grieving, do not hesitate to lean on your pregnancy. Test the waters. It's not about exploitation, but seeing that the grieving goes on and it ate into your planning time which no-one should have to do on their holidays, anyway.
All the best.