The question is rather vague, but there are a few potential reasons you aren't gaining muscle. Remember, these are only possibilities, since it is hard to diagnose the problem off of very limited information.
1) You have not been lifting for a long enough period of time. After two months of lifting, you "might" notice changes in your body, assuming you have been doing some other things correctly (such as the following).
2) Not lifting enough weight. Is lifting extremely easy when you do it? Do you lift for 5 minutes a day or 90 minutes? You said you lift light, well, light might not be working for you if your goal is to gain muscle.
3) Not eating enough calories. I am doubtful of this one, simply because the previous comments are more plausible, but if you do not consume enough calories, you'll have difficulties gaining much muscle.
Hope this helps... edit your question and provide details if you seek a more specific answer.