You are not automatically at fault since your BAC was under the limit, but even when under the limit, BAC can impair your driving. Therefore, the BAC you had, while not by itself proving your fault, will support the idea that you were at fault, but supporting the notion that you were at least somewhat impaired. Add to that that two people (Uber driver and passenger) are both testifying against you (so two to one) and that you were apparently on the wrong side of the road, and is highly likely that you would be found to be at fault.