Quick Hair Loss Question

Last week my oncologist told me "Your hair should start falling out in a couple of days".  So I went home and checked in the mirror - I am fine, I thought smugley to myself.  That is, until last night and I had washed my hair - (it's very short I had it cut 'just in case') I leaned over the bathroom sink and rubbed my hair and low and behold, the sink was covered! "Oops" Well, this morning the pillow didn't look much better, looked like a cat had slept on it (don't own a cat) but that's what it looked like, I took the pillow outside and gave it a good shake - and yes my hair looks thinner I can actually see my scalp already!