falling PSA

I'm  57 years of age and was dx in April 2009, PSA 3.5, GS 6. Bone scan and CT were neg. Started alternative treatment in May, Vit. A,B, C, D3, E, B-complex, B12, COQ10, manganese, magnesium, zinc & selinium. Also Budwig Diet and Aprocot seeds. Also change my diet to veggies and fruits, no sugar, animal fats or carbhydrates. Had a PSA in July, results were 2.2. Had another PSA in October, results were 1.7. My question is are the lower PSA results being masked by any of these supplements or could this be cancer cells dying. Should I have another biopsy at this time or wait and see if the PSA continues to fall?