Even though it seems that all the questions have been answered, I'll throw in my $.02 because I've tried it all.
To start off, let me reiterate what a few people have said earlier- What works for some will NOT work for another. Go on bodybuilding.com and you can find someone who will back up any and every product out there. It all just depends on you. For me, NO Xplode is the best of the NO products. I've tried the complete Universal Animal line, Gaspari line, and even some of the WalMart stuff just for kicks. NO Xplode is honestly the only one that I saw any effects. Workouts were more intense, blood flow was crazy, and I gained weight very quickly.
Some people say that NO Xplode gives them diarrhea. For me, it was the only one that DIDN'T. I always recommend NO Xplode when anyone asks, but remember, we're all different.
And just in case you didn't get a straight answer earlier, if you're just trying to bulk.. gain weight.. seriously, eat everything you see. I can't stress enough just getting calories. Protein is a MUST. YES- Keep drinking your protein shakes. From what it sounds like to me, you have a bodytype like mine- thin, and really high metabolism. If that's the case, you won't get fat, but you have to go to the extremes to gain weight.