Tampon

Im so annoyed and frustrated. I wanted a bath tonight. Im on my period so i put a tampon up and then i put my bikini bottoms on. When i took it out it was full of water am
I not pushing it up far enough ?!?!?! I thought i did it's soo annoying ! This also happens when I go to toilet we is filled the tampon. 
P.S. I am an amateur i'm only 13 please help it's been a problem for a while and i've had enough.