I can't bike standing up and I can't bike without using my hands. I used to be able to do both.

When I ride standing up my pedalling stroke is not smooth anymore. It's choppy and clunky. On the down stroke I bottom out. I see other riders and they're nice and smooth.

When I ride without using my hands I wobble back and forth. I'm able to do it for maybe 5 seconds at most. I used to be able to do it for minutes at a stretch.

Any tips to help me out?