Hey
ridzseeker,
This is actually a lot more common of a problem than you think! So remember that you aren't alone. Here are some things that will (hopefully) help.
1) Many times people will start without a test date -- it sounds like this is the case for you, too! Signing up for a test date and committing to it can help you orient yourself in terms of internalizing that you need to start studying.
2) Also know that your feeling of 'missing the boat' and that feeling of guilt is also really common! Unfortunately there's no good way to combat it other than getting studying and to try to reorient yourself. It's hard, but it can help to be grateful that you had this realization and reached out for help now instead of in a month. It can also help to remind yourself of why you want to take the GMAT and go to business school in the first place.
3) The exhaustion factor. Many people think that the only way to prepare for the GMAT is to get in several hours of study in every night and to dedicate all their time to the GMAT. Not only is this not going to be effective if you have an already exhausting job, it usually ends in you giving up a few days or weeks in. Instead of the all or nothing approach, just resolve to do
something for your GMAT prep for five days out of the week, even if that something is three practice problems. At ORION we've heard from a lot of students that practicing even twenty or thirty minutes a day and setting up a sustainable schedule can be more useful in the long term than going for the all or nothing approach.