6 years is probably too late to reply, but I am another one who finds the sides hurt more. My left hand fingertips are possibly a little callused from years of mandolin and banjo, so that might be why, but I tend to go for the tip, slightly off centre, with the first choice digit being the ring finger.
Dr Bernstein's diabetes solution shows side of fingers (around the tip but not on the pad) but also top side of fingers between first and 2nd knuckle - I never managed to get the top side of fingers to work but might work for you. He also shows little finger and thumb ... tried the little finger but it hurt more than others so did not do that again Any time I have been to hospital they insist on doing the middle of the pad and that hurts
I use all fingers and thumbs to get samples, I start with the thumb and work through the fingers. I then go to the next hand and rinse and repeat. I find this gives the fingers / thumbs time to recover. Last time I was in hospital, I got the nurses to use my Fastclix lancing device instead of the thingy they used.