Yes, Emergency Contraception is definitely appropriate in this case.
It's next to impossible to know when you ovulate unless you've been charting your periods, cervical mucus, and basal body temperature for some time; being on your period is NOT a form of birth control. Nor does it matter how long intercourse lasted -- as soon as semen comes into contact with your vulva there is a pregnancy risk.
Also, both of you are at risk for STD/STIs. It would be a great idea to get tested when you're getting EC.
Finally, intercourse with a tampon in is a very, very bad idea. It can cause harm to your body and trap sperm and bacteria near the cervix.
In the future using condoms would be an excellent idea. They'll significantly reduce your risk of STD/STIs and pregnancy.
Ready or Not? –The Readiness Checklist
Safe, Sound & Sexy – A Safer Sex How-To
Margaret Sanger’s Disneyland - An easy chart of your birth control options
A Simple Condom Primer
A Quickie STD/STI Risk Assessment
What's The Risk? - Five Easy Pregnancy Risk Assessment Flow Charts
[This message has been edited by ookuotoe (edited 04-09-2003).]