Preparing a lecture

I never thought it would be such a pain to prepare a lecture. I am sitting here in a chair that makes my back suffer so much (I once spent 6 hours shopping for a suitable chair: found none, and ended up with the worst pain in my back in years, so much sitting I did) I sit in front of the power point, move my ass to find THE comfortable position (because there is only ONE), look at the screen, move a little bit more, put my leg on the table, it still hurts but a bit better, i can start thinking of the lecture now... Ok, back to business. I have 30 mins already prepared, just 150 more to go... for the first of three lectures. Man, I should have asked for more money. Or a chair. Chairs in university have it all (what an awful joke, sorry)