I am a virgin and naive to many things concerning sexuality. I have a boyfriend now and am curious. Can you tell me how a women's ovulation cycle works? How do I know when I am ovulating? During what time of the month will sex be the most painful?
I am also wondering if certain sports can affect first sexual intercourse. I am a dancer, which means I do a lot of stretching. Can this sort of physical activity wear away my hymen? As dancers, we also have the tendency to clench our butt muscles. Can the tightness in these muscles affect sexual intercourse?
It's not naive to be without information because no one gave it to you.
As far as the ovulation cycle, I sure can! Start by having a look at this: On the Rag: A Guide to Menstruation.
The way to know if you're ovulating -- or, more accurately, to be able to make your best guess -- is to start charting your cycles by taking a look at your cervical mucus every day, and additionally, for more accuracy, your basal temperatures. (If your periods are not yet regular, you'll need to wait to start charting until they are.) If you keep a calendar handy where you can jot down a note about what type of mucus/temp you have, each day when you wake up, you can take a swipe with your finger just inside your vagina to check out your mucus. You'll start to notice that some days will be drier than others, and that some days, mucus will be thicker and pastier, and for a few other days, very thin, clear and much like the consistency of egg-whites. The days where it's the latter are your most fertile/ovulation days. The days where you feel "drier" or where mucus is more thick and pasty are your less or least fertile days. After a few months of doing this, you'll start to notice your patterns and be able to make a pretty good estimate of when to expect ovulation.
Same goes with basal temps: using a basal thermometer (which you can get at any pharmacy), you'll take your temp first thing in the morning and make a note of it. Basal temps usually drop with ovulation, about .4 degrees.
Charting is really helpful just to get to know the patterns of your body, and it can also be used for birth control. It's not suggested that charting is used as a sole method of birth control by couples who aren't ready to handle a pregnancy , but it can be a great backup method for other methods. For instance, to use charting as a combined method with condoms, you'd use condoms at all times except when you're nearing and in ovulation, and during those times, you'd abstain from sexual intercourse completely.
But when you ovulate doesn't have a whole lot to do with whether or not intercourse is painful. Given, during ovulation, the cervix is a bit higher, and cervical mucus is thinner, which can help with lubrication, so for some people, intercourse feels better during those times (though is a far greater risk in terms of pregnancy). But too, during menstruation menses also provides extra lubrication, and more to the point, we always can use extra lube from a bottle whenever we need.
If you're interested in fertility cycles and charting, I highly recommend Toni Weschler's newer book, "Cycle Savvy."
Pain or discomfort with intercourse isn't generally because of what part of our cycle we're in. Rather, it's usually because we're not interested in having intercourse, not aroused or relaxed, going without other sexual activities beforehand, having partners who aren't being responsive to our needs, and so forth. And really, there should be NO "most painful" time. While intercourse can be uncomfortable the first few times you have it, that's not always the case, and the items above are again, usually why a person experiences pain.
For more on pain during intercourse, see, From OW! to WOW! Demystifying Painful Intercourse and Yield for Pleasure. You might also find this piece to be helpful: Sexual Response & Orgasm: A Users Guide.
In terms of your questions about dancing and sports, being physically active is never going to make any sexual activity problematic or worse. It's a stretch to call sex a sport, for sure, but at the same time, it does tend to be enhanced when we're active, fit and in good health. In terms of your butt muscles, clenching them isn't an issue: in fact, doing so can strengthen the muscles of the pelvic floor, which can make orgasms feel more powerful for you and your partner .
The hymen (more accurately known as the vaginal corona) slowly wears away over time, for all people with vaginas. That's due to a lot of different factors: to vaginal fluids and menses, hormones , all kinds of physical activity, masturbation and vaginal sexual activity. There's nothing problematic about that: that's as it should be. But dancing won't do so more than anything else, nor should you have any concerns about the vaginal corona wearing away -- it's supposed to, and it serves no function when it is present.
Just remember: sex isn't only intercourse. Intercourse is only one KIND of sex, of quite a few. You can do your sex life a great favor in advance by thinking about sex holistically, as something that is about a great number of activities, and that is whole body/whole mind. Sex that is just about intercourse tends to very quickly feel like eating the same meal every single day.
Lastly, since you express feeling a profound lack of this information, I'd both invite you to explore the site as a whole, as well as to pick up a copy of my book, which is a great primer: S.E.X.: The Scarleteen Book!