I assume its a stock battery? If this would have been Samsung or LG or HTC or Moto, I would say you typically shouldn't see significant decrease in battery life until a year of use. But Micromax is not a big brand name, at least I never heard of them here in US, and I'm not sure about the quality of their stock battery. Typically replacement no-name batteries from ebay/amazon don't perform as well as brand name ones. Again, I'm just making an assumption and you might had a high quality battery to begin with when you got your phone.
I assume you already checked all the apps you downloaded/installed in the last few weeks since you started to see the problem? Some apps might have been already installed and they just pushed a new update which screwed things up. Also, you have rebooted your phone in the last few week as well? Maybe you have some new widget draining the battery? Could it be a problem with a local 3G cell tower connection? If you switch to wifi, does it drain as fast?
If you rule everything out, battery switch would be the next step. You can get a cheap replacement from ebay which might be OK for awhile, or you can go with a high quality brand name. I just googled your phone, and see Mugen making a double capacity battery for it
HERE. It's pricey, but you are getting probably 2.5x capacity, replacement battery cover (since the phone will be thicker), and the top quality performance since Mugen is very well respected name.
