Retaining the initial friendship post an emotional breakup can be problematic. You're still very much invested in him emotionally, which is completely to be expected. The reason you're overly concerned with his lack of contact is because you still crave that close connection he chose to break off from. His silence could just be him being occupied or possibly being confused on what path he wishes to venture with you now. My advice would be to take a moment and let that hefty investment dwindle in size for a bit. Doesn't mean you can't touch base from time to time, but make an honest attempt to also break off from that close connection. Otherwise you may find yourself going all in on your investment in him and feeling let down by his actual investment in you.

Either way, I wish you the best.