@LovesMyDunnBoy: I have a book that tells me how to both do posting and sitting trot but I thought I was "oh, so smart", and didn't even read the theory on it. I did read it after riding though. In 2 weeks I'll try trotting again. Wish me luck!
1. I was wearing lose underwear and cargo pants (you can fit two people in them
2. I was sitting straight. If anything, I was, from time to time leaning back to balance myself, no way I was leaning forward
3. Work in progress... I hope that by the 4th-5th ride I can at least do posting trot
4. They do, not constantly though. Just from time to time and it's not very painful, like I've been hit. Like a reminder of my ignorance for wearing lose fitting clothes. I will make an appointment to a doctor, just in case