messed up my IMessaging--user manual not helping iPhone

i'm fairly new to idevices and have only had the iphone for a couple of months or so.  anyway, i was able to figure out how to imessage to friends with idevices, but i changed the settings and now when i try to imessage it's sent as a regular text message.

i went into the setting>>messages>>receive at>>   and added my apple id email address--once i added the email addres it said that it was activing imessaging.  now the email address is highlighted and not my phone number, and messages are being sent as regular messages. 

the only "imessages" i can send are the ones i started before i made this change.

is this setting change what's really creating the problem, or is it something else??  either way how can i use imessaging (free) again???

i have turn off the phone, done a soft reset and no cigar.  also i don't have "texting" as part of my phone plan (which was the case when i send the first two imessages), which is why i want to be able to use imessage.  the SMS/MMS features are turned off in settings of messages.

somebody please help me!!!