There is absolutely no possible way to put on 30 lbs of muscle in 3 months unless you started a massive load of test.  

Barring the test scenario, you put on 5-10 lbs of actual muscle,  and the rest via  water weight in your muscles.  Creatine further enhances water retention which I'm guessing you started up given that 30 lbs number.

I have stopped and started lifting many times in my life and I get this effect every time.

I'm not trying to call you a liar or anything, just helping with proper expectations for yourself and others.