Sorry for the delayed reply. I just got back from ODS.
My first 5 months of drilling before attending ODS may have been unique because I was thrown into a role as a detachment officer in charge (OIC) within one of the Reserve naval mobile construction battalions (NMCB). Having had no prior military experience, this has been overwhelming and humbling to say the least, but kind of awesome. In addition to doing all the medical, dental, general military training the other people have mentioned, I have had the responsibility to make sure all the people within my detachment are getting squared away with medical, dental, and training/qualifications, all while trying to learn the system of the Navy.
Where are you on your journey? It shouldn't take that long to get into ODS. For me there was a delay because I missed the boat to get into the October session, then there was a break over the holidays, and the next class (which I got into) began the end of January 2020.