Why do my iMessage's have a subject line in them now?

I have been sruggling with my iPhone 4S all day with the iMessage feature. Somehow I blocked someone that I could iMessage for free thru home wi-fi and tok forever to fix that. Finally I have but now every single iMessage I go to send has a Subect Line in it and if I type in that Line without later moving the icon down to the line below subject, tthen press send , it tries to send but you cant read what is there. You can only read what is below the subject line. It sounds like it is crossed with email somehow???? HELP!!!!