Just took a quick look so far. A couple remarks. First a question: what are your requirements? (output current range, max voltage compliance, acceptable leakage current when off, min rise and fall times...)
The remarks:
* Not sure how you envisioned to use the DRV8837 as a constant current source? Can you elaborate?
* A few parts (like amps/opamps) on your schematic have symbols that are just boxes and make it hard to read. You should use traditional symbols instead, that would make your schematic a lot more readable. As it is, it's pretty hard to guess what it does without a lot of mental exercising.
* Likewise, too many labels IMO. I'm personally not against labels to unclutter schematics (some people hate them), but here some of them don't help readability either.
IMHO, poor readability makes it hard to help you, and may be a reason why you didn't get more answers so far.