my application was like that too - medicals and pc request were very fast (i submitted my application in november last year). after that, complete and utter silence for 4 months. haha. when my application hit the 5th month mark, it became alive again. i got an update in my cic account and then a few days later, received my ppr.
try not to compare your application with others who received their ppr's quite fast - all applications are considered case-to-case basis and at the end of the day, you can't really do anything but wait. i've also wondered how cic process the applications (by reading forums) but just got frustrated. lol. you've done your part - let cic do theirs. based on experience, i would advise you to have lots and lots of patience.