anyone experience very slow / sporadic / little weight gain during second tri? Is it something worth being concerned about?

I'm at 20 weeks and am about 4-5 lbs over pre-pregnancy weight (but I started off about 10 lbs heavier than my ideal weight). I gained about a pound or two during first tri, and in the 6 weeks since second tri has started, have only gained another 2-3 lbs or so.

I have an appt coming up next week so will bring it up to my OB but I was steadily gaining a LB a week with my first since week 13.