Help me determine my activity level?

Yes, I'm aware this question's probably been asked time and time again, but I just have to know. What exactly my activity level?
Am Lightly Active, of Active? While I currently set myself at Lightly Active, honestly, I don't know. From reading responses on other forums and this one results have varied, so I'm really not sure. Now, sure, I could say "sedentary" and log exercise calls as I go... But really - I don't have the time for that.

A bit about me...
Eighteen year old male, looking to put on some lean mass ("slow bulk") and have just started a bodybuilding routine. I currently don't have gym membership, so I work out in my garage 3-4 times a week using two adjustable 10kg dumbells (20kg max on one) and the massive piles of wood and wood bags outside. Now - I don't really do Bicep curls and the the like, I stick to heavy compound lifts (squat/Deadlift/pull up/bench press) and I lift to fatigue, so no cheating in these workouts. Often leads to some mean DOMS.
I also do a good deal of light press ups on rest days, upto around 200 over the course of the day. The only cardio I do is about 30-40 minutes of walking a day.

Now, what is my activity level and- another question - if I am moderately active, do I eat the cals at that number, or raise it higher than that also. Little confused on that matter. I'm a newb.
Reason I ask is because while I am noticing some old strength gains, I'm not getting much on the muscle department. Also DOMS is a *****, and I think I could be under eating and having it effect recovery.

(My apologies for any spelling or grammar errors - stupid IPad)