I saw several well-known instructors to correct my alignment. The instructors cost me a good bit and I wasn't satisfied with the result.
-ALL- of them seemed to think that if your arm is perpendicular to the ground, your alignment is fine.
That has little to no bearing on your stroke being straight. These were well-known instructors that were highly recommended btw. Not to say there aren't good instructors out there, but a warning since it takes a lot of time and effort to change your stroke, you want to make sure you get it right.
I ended up correcting it myself by studying pros and using a video camera. It'll speed things up a ton if you have a monitor you can watch yourself on live while you make adjustments btw. Anyways my stroke mechanics ended up changing a lot and anything to do with control (speed, lines, spin, etc) I had to relearn with the new stroke. It was almost like starting over as a beginner.
It took months of playing for some of those things to become consistent again. I stuck with it though and am much happier with my stroke now.
Hopefully that helps and best of luck!