Why not plan something fun for yourself for your birthday that doesn't include him? Having something other than him to look forward to will help take your mind off of him and how long it has been since he texted you.
Also, do you typically respond right away when he texts? Maybe make yourself a little less available. He's busy? So are you - out there living life right
You are on pretty good ground with him and it seems like you just need to be patient while he works things out in his own time.
BD: Aug 2012 Separated since May 2013 S born Aug 2013 Aug 2013 H agrees to consider 'baby steps toward working things out' H is/was actively seeing someone?