I can put in a tampon anymore? some1 plz help asap!?

i am on the sswim team and i leave in a half hour (i swim from 4:30-7:30) and i just got my period 10 minutes ago. i have tampons but i dont know what to do cause i wore them before and this is the third time i am having trouble. when i go to put the tampon in it hurts and wont go in at all. its embarrasing and i dont want my family to know because they forgot about it already. is there something im doing wrong. is it safe to just swim without something today? please PLEASE please help me. thank you