I used to be a swimmer, so my periods were never exactly regular, but currently I have not had my period since mid December. I have never had intercourse, but I did try anal sex once with my guy right after my last period and we did not use a condom. During the past few weeks I've been itchy in and around my vagina and had more discharge than usual (white)... my thinking is that I have some kind of infection (and I plan on setting up a gyno apt) but I'm too embarrassed to ask... could I possibly be pregnant? I don't see how it would be possible, but missing periods just makes me nervous... and could an infection possibly cause you to miss periods?
It's really unlikely that you're pregnant. It's theoretically possible to become pregnant if sperm on your perineum (the area between your vagina and your anus) swim into your vagina (especially if you're aroused and lubricated)...but the chances are slim. It sounds to me like you've got a garden-variety yeast infection (hallmarks: itching and thick white discharge). You could try self-treating with over-the-counter Monistat, and if you don't get relief, then see a gyno.
Infections don't cause you to miss a period. Many other things can--stress, illness, randomness. Frequent missed periods, though, could be a sign of a hormone imbalance--if you often skip two or more months in a row, it's best to visit the gyno to find out why.
But I do want to take a moment to caution you about anal sex without a condom. The anus isn't built like the vagina - it can't take so much roughhousing, and you're more likely to tear (ouch) or get an infection (double ouch) with anal. The best things you can do for your body with regards to anal:
--ALWAYS use a condom
--ALWAYS use a ton of lubricant, which reduces the risk of tears
--Make sure your boyfriend doesn't thrust quickly or deeply, but has more of a rocking motion with less in and out.
Best of luck,