Missing incoming text messages

My iPhone5 has recently been missing /not receiving a large number of text messages. Friends receive my messages, will respond to me and I never get it. People can't tell I'm not receiving them, and rebooting the phone makes no difference. Ideas? I currently have iMessage turned off because it had caused so many problems for me (can I please just get my ios6 back?) but this issue happens with both iPhone (iMessage) users and non Apple users sending me texts. Right now I'm turning the dreaded iMessage function back on to see if that improves this new issue. Any suggestions what's going on?