Miranda rights are only required when the suspect is: 1) in custody (which would effectively mean an arrest, and 2) being interrogated.
While it seems that you were being interrogated, the issue of "custody" is a very difficult burden to meet. Unless you were essentially already arrested, you will have a difficult time proving this charge. But it will depend on the circumstances.
If Miranda applies, then it excludes statements made and an evidence found as a fruit of those statements. So its arguable whether your addmission to drinking would come in. You should get an attorney to go over the facts in a lot more detail.
One other issue is whether consent was given to search the vehicle. If no consent was given, then there may be an issue with the officers going into the car. Again this is an issue you should speak with an attorney.
This answer does not create a attorney/client relationship, but is intended solely in the court of discussion. It is always my recommendation to retain an attorney whenever a court appearance is necessary. This recommendation is highlighted when it relates to an individual's criminal record.
Miranda may be an issue in your case, but there may also be other facts that need to be researched and investigated based upon the facts in your particular case. You should definitely consult with an attorney to see if a motion to suppress should be filed and argued in your case.