Bulking

I've recently been trying to gain weight "the right way" by lifting and eating a surplus.

I've set my protein to around 1g per lb of body weight, fat to around .5g~ per pound of body weight and carbs to roughly 3g per pound of body weight.

This means that I'm eating 3100 calories in a given day.
(How did I get this number? I burn 2000~ if I don't do any exercise since I'm sedentary. Add in my work outs and I'm burning an average of 2750~ on any given day. Add 300~ calories to that and I came up with 3100 calories.)

Now I had tried eating 2700 before in case I was overestimating my calorie burn and I didn't gain any weight in 2 weeks. I upped it to 3100 calories 2 weeks ago and gained 4lb after one week and another 2lb this week.

Why the hell am I gaining so fast even though I was maintaining at 2700?