It's complicated (OMG, it sounds like Facebook.) We got together when I was very young. We actually met when I was about 8 or 10 or so, and he was a punk teenager. There was no romantic involvement then, we just had a stick fight and my friend and I defended the Fort at the park from this gang of punk teenage boys. Forward many years, I'm in High School, I'm about 15 or 16 somebody introduces us (I thought he was a drug dealer before I met him. LOL! He wasn't.) We started to go out, and things went on and we got serious and monogamous and he had been with other women in the past. He'd been having sex since he was 14, he's older than I am. I was a child when he started fucking girls. Not me, of course, I didn't really see him again after that day in the park until I was in High School. We start to see each other a lot and we started to have sex. A while later, we decided that neither of us wanted to wake up 20 years hence and think (mostly me) "WTF did I miss?" so we had an open relationship for about 6 years, both of us seeing other people. We then closed the relationship when I was almost finished with college, then got engaged; kids, marriage, house etc.
So, he was my first, not my only. I was NOT his first, nor his only. But, we are together now. I'm glad he was my first. Our first time was beautiful.
Not a chance - I started when I was 17 and I've been increasing my number (with stops and starts) ever since.
Although I do envy those people who are with their "first and only" I happen to love the variety of partners that I've had. My insatiable curiosity tends to lead to me getting into all sorts of people's pants, but I certainly wouldn't trade that for a life of monogamy. *grin*