I'm posting this here just in case other prospective female cadets have the same questions.
Summer Training:
Not to fear, it isn't as huge of an issue as you might think. Bring tampons/pads with you to R-day or I-day. You can have your parents send you more but keep in mind, your packages may be inspected by your squad leader when you open them. Mine were. This may bother some girls, so it's up to you. During Beast, you have opportunities to visit the C-Store and restock. Just be prepared: they have a limited amount of brands. So, if you have a preferred brand, bring your own supply (2 weeks) until you can check out what the C-Store has to offer. If you find yourself in desperate need of restock and can't, ask one of your female cadre members for help. She will be more then willing to help you out. I imagine it's the same at Navy.
I never had issues during Beast or other training events. Most of my other female classmates never did either. We were always allowed enough latrine breaks to where we seldom had to request an extra visit. I just carried supplies in a zip-lock bag in my ACU pockets, ruck and camelback. That way, I was always prepared. When I was out in the field, those supplies would also include hand sanitizer, extra toilet paper and the little moist towelettes you get in MREs. These extra supplies were a lifesaver when there was no toilet paper (an often occurrence) or running water. If you suffer from cramps, bloating ect., again, seek out your nearest female cadre member. She'll be more than happy to get you some Midol or Advil.
School Year:
Definitely don't need to worry here. Unlike Beast, you can use the restroom anytime you like and without permission. You're also allowed to go to the C Store by yourself. However you deal with your cycle now is how you'll deal with it during the academic year.
Alternatives:
I know some of my classmates who just took birth control prior to Beast so they wouldn't have to deal with it. Some take it during the academic year as well. It's up to you and your doctor. It takes a couple months for your body to react to the hormones and for you to find out if you're compatible with that particular form. Some women have to try multiple times before they find one that's compatible with them. You may or may not be willing to play that trial and error game before Beast.
I hope this sheds some light on your questions. If there's anything else you want to ask that you may not be so comfortable asking over the public forum, shoot me a PM!
Extra reference:
This thread was written in 2006 but still extremely relevant today:
http://talk.collegeconfidential.com...8-minority-report-girls-guide-west-point.html.