Kent is right... on eway of explaining that for every new thing that happens, there will be a little fresh pain as you learn how to adjust to the new thing, as you grieve fresh for the new situation.
But luckily, the grief process is quicker with every new thing that arises.
A year & a half & you're not ready yet? How long were you married and how did the breakup take place? Are you (or were you) harboring hopes of reconciliation, fantasies that he'd be there if you could figure out how to work your way around to it again? Maybe he did things that encouraged you to believe this or did not discourage you from it?
It took me a long time to recover and really be ready to date, but I was dating before I was ready... not like there was any reason not to other than that my mind was a mess. I did not harbor feelings of reconciliation so much as my ex messed up my ego to a point where I had a hard time thinking anyone would ever want me. It took a long time for me to understand that he was a mess and he had to make me feel like a mess just to make himself feel better. Once I understood that, it got easier.
I guess what I'm saying is that there are lots of reasons for being ready to date, lots of reasons a person would not be ready. But a year & a half after the divorce is final is kind of a long time to be experiencing it this freshly, so I'm wondering if there is something more behind it than straightforward grief for the loss fo the relationship... .