An increase in physical activity. Increased body temperature, which makes you sweat more. A decrease in appetite and irregular or unbalanced diet. If your periods do stop you can still get pregnant. If you are sexually active, use contraception.
Condoms are most effective in preventing sexually transmitted diseases AND pregnancy.
This will combat dangerous dehydration as well as help reduce the bloated feeling that can accompany water retention. If you are having a painful period don't use drugs to mask the discomfort. You will probably end up feeling worse in the long run. Go a little bit easier with yourself than you normally might. Remember wherever you are going may not have a sanitary dispenser.