If your scores continue to decrease, it may be best for you to reschedule your test date. If you're taking a mixture of tests offered by Kaplan, Princeton, and the AAMC that could explain any inconsistency or decrease in your scores. Students tend to score higher on Kaplan exams, lower on Princeton Review and it depends on the AAMC test. I recommend sticking to one method to see consistent improvement, taking the tests in the order recommended by the test prep company.
Two or three weeks may not be enough time for you to see an increasing trend in your practice exam scores. If possible, give yourself more time. Don't forget to take a few days off before the actual exam to give yourself a break. Remember to breath and create a timeline based on your new test date. Take it one day at a time. Use your practice test scores to guide what you study each day. By consistently focusing on your weaknesses you should gradually see an increasing trend in your practice scores.
I am attaching a link
here to an article with "5 MCAT Prep Tips." I hope it's helpful!