Hi there! Seems like an odd problem you are having. Here are some basics for turning that may help:

Applying pressure to your toes will allow you to turn in the direction your toes are facing. The board will tip slightly in that direction and the board should smoothly turn. To stop making the turn simply center your balance on the board, keeping your feet flat. To turn in the opposite direction, put pressure on your heels and your board will tip back to make a smooth turn toward your heels.

It is possible that the trucks may be too tight making turning difficult. Loosening the large center bolts on the trucks will loosen the trucks making the board more responsive to weight shifts for turning.

To ensure your trucks are on correctly, check out this guide: Skateboard Skateboard Trucks Replacement.

Hope this helps. Good luck!