I assume you are using a release. I switched to a release (WinnFree SS) from a (very,very long time) two-fingers-undertabrelease this past February, and had a difficult time with the switchover, including holding steady.My old anchor point with a tab was no longer viable with the release. I finally found a way to anchor that helped me steady-up: by puttingmy thumb behind my neck. This approximated what my thumb was doing under my jaw bone when I used to shoot fingers, and the release hand no longer seemed to "float" as it had, in spite of mybest efforts to develop a solid anchor point. So I do not know if the technique can help you, but it may be something to try. Having a consistent, comfortable anchor point was the key.
Ditto on weight training - a balanced program three times a week to keep your upper bodyin "tone" should help.
-fsh