Will excessive exercise cause my periods to stop?

[Leia]

i've been training for navy boot camp for the past two months and my periods have been extremely light and have lasted 3 days. before they were very heavy and lasted up to 8 days. is this a bad thing? will it affect my hormones etc? i ship off to boot camp in two weeks and after that am going to personal training school so i am going to be exercising like crazy. also, my skin has improved greatly, like no blemishes etc. i usually break out around my period but since i've been working out, this has also stopped. i jsut want to make sure my body is not going to be thrown out of wack. any experience or advice? thanks