Difference between zakaah, fitrah and sadaqah

Q: I am listening to a lecture here at work and just determined or realised that there is a difference between zakaat, fitrah and sadaqah and I realised that I don't think I pay zakat? I feel so ashamed now as I was so ignorant to this and I would like to rectify this immediately. I tried to Google zakaat now but its a bit confusing. So if I may, can Mufti explain to me the difference between the 3 and how do I calculate zakaat and when I must pay it. Your guidance and assistance is greatly appreciated.

Bleeding after a miscarriage

Q: I was 11 and half weeks pregnant and started brownish spotting. I went to the gynae who couldn't find a heartbeat (they refer to it as a missed miscarriage as I had no symptoms of a miscarriage). Few hours later I had a heavy flow and the next morning went in for a d&c (scraping of the womb) please advise if this is istihaaza?