Low BUN - Liver problem?

I had some blood work done a few days ago and am quite concerned because by BUN was low (3.5 mg). I recently have been on Vicodin ES - 1.5 tabs 3 times daily for 4 weeks for a miscarriage and D&C at 14 weeks pg. (I have also had several pelvic surgeries (5) in the last 5 years)My ALT is 10, AST is 14, Alk Phos is 72, Bilirubin Total is 0.3, Creatinine is 0.7, Total Protein is 6.6, Albumin is 4.0, Globulin is 2.6, Calcium is 9.8, Sodium is 140, Potassium is 5.2 (is this high???), Chloride is 105, and Carbon Dioxide is 25.6. A/G ratio is 1.5 and BUN/Creatinine ratio is 5.0! Urinalysis was normal. I have also been taking Vicodin ES regularly as perscribed by my doctor for 5 years because of the surgeries(never more than 4g per day and NO alcohol - I am 5'4 and 112 LBS). I have also had recent diarrhea for about 7 days. I read low BUN can mean LIVER FAILURE! Could this be the case or would the other Liver Function Tests be off?  In the past 6 months I have had EGD, Colonoscopy, Abdominal X-Ray, Abdominal CT, Brain MRI, and Small Bowel Follow Through - all these came back fine.  Please respond, I am a basket case over this.

[imkindly]

BUN stands for "blood urea nitrogen", a waste product normally excreted by the kidney.
Your BUN value represents how well the kidneys function.
BUN reflects the kidney