J.L.
Hi, my 3 year old daughter has the same problem. She got her glasses about a year ago. Her left eye crosses. We moved here last fall and I just took her to the new pediatric opthomologist. Where we lived before they had us using a patch for two hours a day to strengthen the eye that was turning in.
The doctor we just saw is trying a stronger prescription and says if it doesn't work then we'll have to do surgery. If that's the case then we'll have to get a few other opinions before doing the surgery. It was hard at first getting her to wear glasses and getting used to it but now its as if she always has worn them. Best of luck to you.