I have never used sub myself, but have some understanding of it from my time here and from my own withdrawal experience from Oxycodone.
That motivation WILL come back and don't doubt it ever. It is a slow, baby-stepping process. Keep pushing the physical activity and forcing yourself to do something regardless of how little motivation there might be. Often , we can not recognize the progress because we are hoping so hard for it all to be normal again. Might be helpful to chart any and all acomplishments each day... I did that for quite a while. When I looked at my chart, I could see in black and white that I was doing a bit more each day. It countered the thoughts that I was going nowhere.
I think by the time another two weeks passes ( and I know that can sound like forever), there will be a big hunk of progress made in feeling more like what you are waiting for.
From all I have read, the jump from Sub at 2 mg is still a jump from a pretty high amount. Give the brain and body some patient time. I wish you all the best.
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