Got Arrested Need Help!!!!!!!?

im 22 i dont do drugs or drink i dont take painkillers , so heres the story , its truthfull too thats the funny thing, so i was driving my gf's car with my friend to take him to go see his dad at jail for visitation , and as we pull up to the jail the k9 crew comes out and searches the car which i had no problem with cause it wasnt my car , so they searched it and found 2 vicodin in a ciggarette pack , now i smoke but they wherent mine , they where my moms pills she barrowed the car the day before and said she dropped some but forgot them in the car, she is precribed them ,and i got arrested and she posted my bail at 10% of 5000, now im out and she tryed telling the police that it was hers and wants to show proof, but they think im just a druggie and they dont belive her , how would i go about all of this? i live in port saint lucie , florida