If you have had an orgasm you'd know. Do you masturbate? If not you need to, to find out what feels good. A small vibrator can help.
Don't worry about tightness. It is what it is. People have babies and it returns to normal. Don't worry about that.
The white is a mixture of discharge (normal) and vaginal lubricant you produce when turned on. It's normal.
Every bloke is different after orgasm, some can keep going some go soft. Not your fault or doing.
You are over-thinking and that's bad. Concentrate now on what gets you off then you can show the new guy.
(use protection)