A week or so is typically not enough time to make enough improvement that you would notice any big difference in practice test scores. So, basically, you're taking the tests too frequently. :)
On the other hand, you've been studying for 3 months and haven't seem much improvement over that entire time, so something is going on, yes.
Read this:
http://www.manhattangmat.com/blog/index ... -the-gmat/There are links to lots of other resources within that article; make sure to follow them.
In terms of getting specific advice here, I'd like to get some more detailed data on your strengths and weaknesses in order to advise you. Use the below to analyze your most recent MGMAT CAT(s):
http://www.manhattangmat.com/blog/index ... ice-tests/Then come back here and tell us the results of your analysis and what you think you should do based on that analysis. We'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)
Note: do also read at least the main Studying and Struggling article before you reply. That will help you to formulate your ideas about what has been going wrong so far and what you need to do about it.