Hi, flower,
I am 64 yrs old, been married now 29 yrs, been through a lot, even a Divorce many years ago.
You really have a lot of thoughts, and have a lot of questions about getting married to this person. Your sexual relationship seems normal to me. Talking about sex, what you like, don't like, with your partner is a good thing.
But, are you ready for marriage? How old are you?
If you are younger than say, 22 yrs old, I would wait awhile. The Divorce rate in the US is now over 50-50, over half the marriages end in Divorce. If you are younger than 20, it's worse!
You need some time, time to decide what you want out of life. That's what dating is all about. Discover new people, and find out, for sure, what you want. I do wish you the best.
PS; I was with my first girlfriend for 6 years, thought we were going to get married eventually, after college. Wrong! She found someone else.