Accurately, you'll have to go to a sport's medicine place and get some tests, but that costs money and that level of accuracy is unnecessary for deciding to bulk or cut.
If you want a ballpark, there are a few different methods. There's comparing yourself to pictures: http://www.builtlean.com/2012/09/24/body-fat-percentage-men-women/
There's bodyfat calipers: http://www.amazon.com/gp/product/B00B2MIDFY/ref=wms_ohs_product?ie=UTF8&psc=1 This didn't work out for me because I'm squeamish and hate pinching my skin under fat and stuff.
There's impedance meters: http://www.amazon.com/gp/product/B000FYZMYK/ref=wms_ohs_product?ie=UTF8&psc=1 The theory is the more fat you have, the more a current is impeded as it flows through your body.
It may be worth it to get a body fat monitor to keep track of, and map that versus your weight. If you start to accumulate fat, you may want to up your cardio, and cut some calories.
20 pounds in 2 months is great. If thats what you intended, of course.
edit: that bot is the coolest
Bioelectric impedance can very accurate as well: http://www.amazon.com/Omron-HBF-306CN-Fat-Loss-Monitor/dp/B000FYZMYK
I started it around the same time I got a bioimpedance fat loss monitor, which was in April. According to it, I've lost almost 10% body fat since then. I don't know how much I trust the monitor but honestly, I love the E/C stack for its appetite suppression. I cycle on it for 8 weeks and off it for 2 weeks. I can tell the difference when I'm off it, hunger wise.
It's nothing crazy but when I'm on the E/C stack, I have to set an alarm to remember to eat when my feeding window opens up. That's pretty useful. I could live without it but the appetite suppression + fat burning makes it pretty worth it.
It makes some people jittery but I have no adverse reactions personally.
Awesome, good luck with the cut and stay focused on your goals. Im almost certain in that photo I was around 160 but if Im off it'd be around 163 max.. And with the body fat % I had done it the day that photo was taken. I used this this measuring tool