I always gained in fits and starts. Like some weeks I was up several lbs, and then other weeks I gained very little. I would try not to focus too much on the week to week or month to month thing, because IME that isn't very predictable. I think it is good to have an overall feel for how things are going...if you are gaining fast and know you are horking out, it might be a clue to dial back. Eating healthy, baby is growing, care provider isn't concerned, and you gain more than you expect a few weeks? I wouldn't stress as much.
I am not a large person and gained exactly 38 lbs with each pregnancy, even with eating healthy. It was like a predetermined set point for me! The weight always came off by a yr or so post partum.
Mama to DS-2004
DD-2006
and a new addition-ds born march 2010