Why my MBPr wireless connection is slower than when I purchased it on July?! Weird...

Currently it bother me soo much that I need to post this here in hope for some solution is available....

Wireless speed SLOW! comparing when I use my MBPr during July (same place, same environment, same connection speed, same provider, same equipment, and location) It just acting weird since I have 16Mbps of d/l home internet speed but when I perform speed test I got smth. like 1-3Mbps...

Please kindly suggest any opinion will at least generate an ideas of what I need to do to fix this MBPr I used to really love it...