I am 17 and have just recently become sexually active in the last 2 weeks or so with my boyfriend. The first time I had sex with him, I bled a little, but I know that was normal. Over the 2 week period, we had sex about 8 times or so and i didn't bleed after that first time. However, the last time I had it with him, I started to bleed again, significantly more than the first time - it seemed as though I was getting my period early or something, but it has now been 10 days since that event and I haven't gotten it. We haven't had sex since then. Also, it still hurts to have sex (though not to the point where we have to stop), and my boyfriend is not exceptionally big or anything. So I have a few questions:
1.) Is there any explanation for the bleeding thing?
2.) About how many times on average will it take for sex to start feeling good for me, and not hurting?
Also, about how many days
after your period
ends(as in the actual bleeding) are you the
least fertile? The cycle has always confused me a little.

I usually get my period around the 24th of the month and it lasts for 5 or 6 days. I'm usually not on a regular cycle though, and have a tendancy to skip a month sometimes. I would just like to know about how many days after you are the least fertile for an extra precaution as to when I'll have sex. We use condoms always, but I'd like to know.
Thanks to anyone who can help with any of these questions!