Underage consumption Tennessee

I was driving home some friends who had been drinking. While I was pumping gas, they got a little loud and attracted the attention of the police. We were all arrested. They all got Public intoxication charges, while I was arrested for underage consumption. I'm 18. The police said they only have to smell beer to arrest me. I asked repeatedly for a blood alcohol test. Of course they are going to smell beer, I had a car full of drunk people. My mom showed up at the police station and was told the same thing. The officers told her she would be able to bond me out within the hour. She was chatting with them and said she was taking me to the hospital after she got me out to get a blood alcohol. They asked her to leave and put a "hold" on all of the people arrested including me, so that we could not be bonded out. So, I had to go to jail and go before the judge at 9am, then wasn't released till 12pm. Any testing that could have proven I had no alcohol in my system would have been useless by then. We don't think we need a lawyer, but I'm wondering if anyone has any advice.