Honestly I feel like there are 2 important factors here that we need to look at...
a) you've taken this medication for a very long time with no break.
b) your taking a very low dose and as prescribed.
Clearly if your doctor is stopping the meds cold turkey
you'll live. I mean he must understand the concept of WD. However I personally feel that you'll have some minor WD symptoms.
b) pain in the area you were treating
These are minor in the cases of WD from opiates
. Honestly what I would do is take those last 20 days worth of medication and make them last a full month. So lower your dose down and possibly start titrating off. This way I'm very confident you'll be fine and suffer no symptoms.