Should i be getting a JR PASS

Hi,
It's almost covered by going to Osaka and back. You need a couple of side trips to break even - you could easily do it by seeing Himeji with Japan's finest castle for a day. Or go see Nikko for a day north of Tokyo. Or go visit Nara for a day, and do some sightseeing in Kyoto.
You can use the Pass on the Yamanote Line in Tokyo, as much as you want for as long as the pass is still valid. In Osaka you can also use it on the loop line. For Mt Fuji you cannot go all the way there on a JR Pass. If you'd like to see Hakone, there is a Hakone Free Pass for that. And if you want to go to the Fuji 5 Lakes area, there is a regional pass for that too.
You could spend a lot of time in Tokyo and still not see everything. But a few of the best places to see are the Tsukiji Fish Market, plus the site that every last tourist goes to see, the Sensoji Temple. If you are in Tokyo on a Sunday afternoon, be sure to go visit Harajuku to see the youth with their wild fashions. Meiji Shrine and Yoyogi Park are next to it and well worth seeing also. And be sure not to miss the Shibuya Hachiko intersection especially on a weekend when it looks like half the city is crossing the street at once.

Best of luck.