You've got two separate issues - the DUI and the search of your car.
First - the search. Let's assume it was a completely illegal search. The remedy is that any evidence they found would be suppressed (thrown out) and not used against you. Assuming they didn't find anything incriminating, there's nothing to suppress and the search issue may to impact your case.
Second - the DUI. It's difficult to evaluate anyone's case based on a paragraph on the internet. I'd suggest you sit down with a local criminal defense attorney to discuss the case in greater detail and explore what options and defenses you have.
Keep in mind that you only have 10 days from the date of your arrest to contact the DMV to fight against the automatic license suspension they will impose.
If I understand the facts, the officer cannot legally search your car -- other than objects in plain sight -- without an arrest. The purpose of field sobriety tests is exactly that: to help determine whether probable cause exists....As for swerving, this "observation" is widely abused by the police, as all cars swerve within lanes to some degree, and often more pronounces swerving is due to "black-and-white fever" -- taking your eyes off the road while watching the police car in the rear view mirror...The arrest report should show how you performed on the FSTs; if it doesn't, the officer is subject to attack in his testimony.
My colleague has given you good advice. I urge you to immediately find an attorney who has a practice focus in DUI/DWI. That attorney can guide you through this entire process and do you a great deal of good. There are many issues here that you did not write about and that an attorney can ferret out in a consultation.