GIRLS only HELP need loads of answers read inside for more please answer i need really good advice. :)?

ok so am on my period nearly at the end so thats when it starts to go brown and thats normal as far as i'm conserned but the funny thing is starting to smell real bad like unbelievably bad no no it didn't smell fishy like normal it smelt odd and really bad, do you think that when i go it the shower this smell will go i'am putting on a freash pair of knickers and a fresh sanitery towel on to, do you think this will help or is there something wrong with me. plus i didn't feel to good either when i went to the toilet. HELP and please don't be silly about this i'm kind of worried. what should i do? any ideas oh and btw i'm 13 year old female nearly 14, i've never had these sort of sign's before and i have no idea why it is smelling so bad.