How to keep crochet work from curving/curling?

I am crocheting a simple scarf out of relatively bulky yarn. I am using an I size hook because this is what the project calls for. I took advice from another forum and used a slighter bigger hook (size J) to make the foundation chain a little looser, and this helped with the beginning of the work, but now that I am working on different rows and doing different stitches and building on the scarf, it is starting to make a very sharp and noticeable curve to the right. What can I do to stop this? Is there anything I can do to prevent it from curving or just finish the scarf and modify it somehow to make it less noticeable? This happens from time to time with me, and it annoys me so! It doesn't happen all the time--only with certain patterns and fabrics, and it happened with a scarf I made for my husband, and even he noticed it and could tell the difference, and he doesn't know the first thing about crochet! lol Any suggestions would be much appreciated. Thank you!!