Hi Smiler, nice to see more teachers pg with their first! I am a teacher (Early Years like Ceebs), married, 27 and expecting the miracle child the doctors told me I would never have (cue a very smug look from me, tee hee!). I am now 28 weeks and finding it impossible to believe I have less than three months to go until I am a mummy... My maternity leave begins in 3 days and work have actually been pretty good on the whole - my nursery team have been very understanding and my nursery assistants picking up some of the slack re: heavy lifting etc. My headteacher was less than impressed but lately even she seems to be caught up in cooing over my lovely bump 
I promise it does get easier - the weeks until your first scan seem to take FOREVER (it didn't help that I found out I was pg at the start of the summer holidays so had six weeks off to worry and stress about it all!), but once you have that scan it makes it so, so real... the most amazing moment of my life, I'm not ashamed to say I bawled my eyes out with relief (having had 3 prior early mcs).
I told my parents about two weeks after I found out - I gave myself a bit of time to get my head around it (and convince my husband it was actually happening this time), and then I told them after having been for an early scan. They were over the moon. Yes it is risky, but if anything should go wrong (which it probably won't!!!), I think I'd rather have my parents in the know and ready to support me and pick me up than have to deal with my emotions on my own IYSWIM.
Anyway, sorry for the long ramble, just nice to read a happy familiae story. Good luck with everything, keep us updated :)