What is the worst thing than can happen to me for this Underage Drinking case? PLZ help!!!?

I got pulled over 2 nights ago with 2 of my friends(over 21) The officer asked me to step out of my car and gave me the sobriety test which I ped but appearently I blew .04 but he didnt even show it to me and I did not confess that I drank. I only had 2 beer. He gave me a ticket for consuming alcohol in penger seat but i was not and my friend plead guilty for that, the fine was 530. He also gave me citation for possesion of alcohol under the age of 21 but it was not even my beers it was my friends and he told them that, there were 2 empty can under my feet which where emty and dried. Here is the law in Maryland It is illegal to drive or attempt to drive a motor vehicle with blood alcohol concentration of .02 or higher. Violations of the above law are misdemeanors, subject to fines up to $500 and suspension or revocation of driver's license. Should I get a lawyer or is their case even strong enough to suspend my license. He let me drive home after 30 minz. Serious answeres plz!!!