It'll underestimate in your case because you are at a light weight and a low body fat %. Instead of using Harris-Bennedict, use the fat free mass formula. This gives you...
Your RMR is 1908 Calories per day. Formula: RMR = 1.3 * Fat Free Mass (in kg) * 24
Now multiply for a moderate activity level (1.55, assuming you are doing no cardio - and you shouldn't be! Though walking and daily activities and such are fine, if you do a lot of them you need to factor them in and raise calories even more) and you get 2958, about 600 calories higher than what you were likely getting. This means that you are eating at only a slight surplus, assuming this formula is dead on (and chances are it isn't, because they're only guidelines based on theoretical averages).
You obviously have a big ass fire inside, so that isn't gonna be enough. I'd say push it up to 4000 and see what happens. Though as others have said your complaining about your gains is completely ridiculous. That is fantastic progress. But you may be a mutant who can do even better, so eat even more! Reevaluate every two to three weeks with photographs, measurements and how fat you look/feel like you've gotten. Leave calories alone or decrease a little if/when you feel like you are suddenly eating enough to put on some fat in addition to muscle.
Edit: Also, what are you doing in the gym? If I had to guess from your physique it'd be 8 sets of 100 crunches each and nothing else?

Kidding, but seriously. Nutrition is most of the game, but you don't want to be developing imbalances either. Or if they're natural, you want to be proactive in correcting them.
I notice you've only provided pictures of your "bar muscles". You know, what's on top and can be seen from the front. What about the back? Your lower body?