I turned symmetry on and when i paint straight on one side, the other half is curved. Any help?
Without pictures it’s hard to say for sure. But make sure that M is turned on in the Transform>Symmetry choices. If it’s not, the effect will be in the same direction on opposite sides of the mesh instead of being mirrored across it.
Also, make sure that the object’s center point is its geometric center. If its local coordinates are off, so will the symmetry be.