People on SB always recommend "go diving" and while I certainly agree with that (especially over taking a dive master class at your experience level) sometimes it is not quite that simple. There *is* also something to be said for getting experience by taking classes
There is: After you have some experience.
If you don't feel comfortable going diving after your open water course, go back to the shop and demand your money back (or more instruction). Then go diving - a lot. Get 30-50 dives under your belt, then go back and get more training when you have some actual experience to draw upon.
OP - what is it that has given you the indication that you are a "Master Diver" candidate after just four months diving? Given that this is an activity that some people dedicate their lifetime to, doesn't it strike you as odd that such a designation is available to you at this point in your diving career? Shops are there to sell you things. You're being sold a fabrication at this point.