Not quite in your same boat as I was a CEC DCO, but I will say that I got my pro-rec at the very end of May and my COMDOCs came in at the end of July/beginning of August. I had already completed MEPS and had a Secrete clearance for my civilian job. I would imagine that with the shake ups in the CEC/Seabee communities along with the government shutdown that FS letters are a bit slow coming out. When did you complete MEPS/submit your SF86?
As much as it sucks, patience is a virtue.
Edit: Remember that right after OCS you need to attend CECOS at Port Hueneme. Right now there are only 2 classes a year. The next one is starting 27JAN followed by one on 7JULY. I would hazard a guess that in order to keep the pipeline streamlined you will get orders to OCS in time to make one of the classes pretty close to your OCS graduation date. So, if you haven't gotten your FS yet, you might have a couple months left to wait so you could start in March and roll right into CECOS. This is, of course, pure conjecture on my end. It seems logical though which likely means it is completely incorrect!