Not knowing if my period is still here? Help?

I'm going to the beach today with my class and I woke up today and there wasn't any blood on the pad. Today is my 5th day, I should have it really light, but sometimes it's just not there. I want to wear a tampon, wearing a pad isn't an option at the beach. But I don't want to put a tampon in if my period isn't even there. Please help. Thanks