Most Helpful Guy
If you are just inquiring about the blocking/ unblocking part, the answer is simple. He misses you, then he remembers something happening (a fight?) then he misses you again. It has no significance, believe me. It may be that he is having second thoughts but till the time he actually does something about it you shouldn't let it affect you so deeply.
Many a times when relationships cease to exist people miss each other. If the relationship got over at a very silly point, all it takes is an apology and understanding to bring it back. But sometimes we figure that what the relationship gave us wasn't much and it's best to be with someone else. It'll be your decision :)