Want..to...flame...must...resist...
I went in to OCS not exactly a push up king myself. Like you (I assume) I was knocking enough out to make the cut, but wasn't by any means maxing it out. My push up score went up every pt test simply because we were doing push ups all f'ing day. Your score will improve, so don't panic if you aren't great at it yet. Getting your numbers up before OCS is a good idea though.
How is your form? Inconsistant form could very well give you inconsistant numbers. When you practice, have someone to watch you to make sure you are doing them correctly. 100 sh!tty push ups (head bobs) take as much effort as 30-40 real, OCS style push ups. Good luck. OCS only sucks for the first 12 weeks.