Berberine is not something to fool around with. It does seem to work to some degree, but it may do so by affecting your liver in potentially dangerous ways. See, e.g., http://diabetesupdate.blogspot.com/2013/08/berberine-works-but-may-very-well-be.html. It has not undergone the rigorous testing process to which all FDA-approved prescription drugs are subjected.
My history was very similar to yours. I was eating a very low-carb diet and exercising regularly, just as you are, and had similar fasting blood glucose, post-prandial glucose and HgbA1C numbers. I was never diagnosed with full-blown diabetes (those levels are higher than the ones I exhibited), but it was clear I was pre-diabetic. Pre-diabetes is not a benign condition. Pre-diabetics experience serious cardiovascular events (stroke and heart attacks) at significantly higher rates than those with normal blood sugars, and about one-third of pre-diabetics progress to full-blown diabetes. It became clear to me that diet and exercise alone weren't going to give me normal glucose levels.
I went on Metformin and it enabled me to achieve truly normal blood sugars. You may want to consider discussing this with a doctor with experience in the treatment of pre-diabetes and diabetes. You won't regret it. For further general information and discussions of treatment protocols for pre-diabetes and diabetes, see http://www.phlaunt.com/diabetes/ and Dr. Richard Bernstein's book, Diabetes Solution.