WP automatically adds BR tag- how to disable?

Hello. I just upgraded my version of WordPress and, after the upgrade, all line breaks (in posts) are converted to BR tags. However, I do not want this conversion to take place. How can I disable this conversion- I seem to recall an option on the previous version but can’t find it on 2.2? I have a lot of HTML in the previous posts that contain line breaks, which is now broken with the random BR tags.

Any help is appreciated. Thanks.