Trouble highlighting text in post editor

I just had this problem happen and not certain what I did, but I believe I hit a key on my keyboard (or combination) and now I can no longer highlight the text while editing my posts. I also can’t resize my photos within the post as I did before. I’ve tried going back to an earlier revision before this happened, but the problem still exits. This problem only happens while using WordPress. Any ideas or suggestions on how I can fix this? Super annoying being I can’t highlight anything to delete, add links, etc.