9 Months and supplementing with formula

My son is 9 months old and I've been EBF up until 3 days ago.  When I first went back to work I was still producing like crazy and had a HUGE freezer stash.  But, sadly in the last 6 weeks My supply has almost diminished and I've tried everything to bring it back but it's just not rebounding so I've had to start supplementing. Don't get me wrong, I'm so happy my son is happy and healthy and fed, I'm just mourning the fact that soon we won't be nursing and having the special time together anymore. :(. Any one else having this issue as well?