Still losing, but not trying!

Ok, this might sound like I'm trying to brag or something but that is NOT the case AT ALL! Allow me to explain, I am a 36yr old man 5'10" tall and back in February I weighed 180lbs, not fat but not where I believed my ideal weight was so I started a modest training program using an Xbox Kinect game 30 minutes a day, three days a week and lost about 10lbs. Then I discovered the myfitnesspal app for my Android phone and started keeping track of what I ate religiously (my diary is public BTW in case you want to glance at it) and lost another 10lbs, so by June/July I was where I wanted to be, floating between 156 and 159 depending on the day.

I might be getting a little paranoid and jumping the gun here but in the last three days I've made a couple of changes to my daily "diet" (I used that word only to define what I eat during the day, not because I consider myself ON a diet) which amounted to ADDING more calories in the form of a lean protein shake with my toast and peanut butter with my morning snack and another one with my almonds and raisins with my afternoon snack and I have dropped TWO MORE POUNDS and as of this morning I now weigh 154.5.

If I am to gain weight at this point I want it to be muscle, I don't want to stop working out and eating more or eating less healthy just to add fat to my body. I'm hoping there's a trainer or nutritionist reading this who might be able to point me in the right direction here. Should I just up my workouts? Will that cause my body to start growing muscle weight? Is my metabolism so fast now that I have to add even MORE calories in order to allow my muscles to grow or will my body start to store it as fat because it'll be too much excess?

Someone please give me a little guidance.