Metformin and PCOS

I just got diagnosed with PCOS. My doctor prescribed me metformin and letrozole. I am supposed to take 2 pills of metformin a day. One in the morning and one in the evening. I took one whole pill last night and am already feeling the side effects (diarrhea). Do you think it's ok to start slow by only taking one pill a day (half in the morning and half at night) until my body gets used to it? Or would I be more successful taking 4 halves a day ( half in the am, half at lunch, half in the afternoon, half at dinner)? Any input on how you got your body used to metformin to help with the side effects would be greatly appreciated!