really need to know just what you are doing- and what is not working for you in order to help.
i do lots of curved piecing, but need to know just what kind of curves you are working with-
could you post pics showing where your problems are occuring? if we saw what you were doing we could probably help.
if working on drunkard path's or NYB blocks--the concave piece needs to be on top (the outer curve-on top the inner curve) ( =convex )=concave concave piece on top of convex piece- match centers and outside edges. then lots of pins distributing evenly along the curve. stitch slowly, removing pins as you go along- stopping every few inches, with needle down- pivot a little then continue-
i hope this helps a bit- pictures, specific questions and we can help further.