Worried about low weight gain

Hi everyone, I'm 20 weeks along, and nervous about how to increase my intake and gain weight. I'm 5'3" and started out at 115 lbs (52kg) and lost 5 lbs because of first trimester sickness. I just weighed for the first time in 3 months and am 117 lbs (53kg). My belly looks like I think it should (definitely reshaped and very obviously pregnant, can't see my feet anymore) and baby is estimated to be 10oz. Doctor didn't mention the weight at all, and when I expressed concern they said it's good I'm up from my original start, and to try gaining 1 pound per week now.

Getting enough calories in has always been difficult for me. When I started tracking at beginning of pregnancy, I was very under-eating by accident (I don't feel hungry very often and feel full easily) and am pretty active. I've been trying really hard to increase my calories the last few days since my appointment, but even pushing myself to eat more, or add calorie-dense foods, I'm still barely hitting 1800 when my estimated need is around 2000. I don't know if I should just start eating dessert everyday or a bunch of pizza or what.... but I could definitely use some advice. I feel like I'm trying to force-feed myself already, and I'm very uncomfortable.