Weight Gain Advice?

Olivia • 22 years old, single momma 👣 Dominic A. was born April 28, 2016 👶🏼
So I'm 21 weeks now and with each checkup with my Midwives, I've noticed that I don't put on any weight! I was sick constantly for the first three months but now I cannot stop eating. I have maybe put on 2-4 lbs. since being pregnant. I've always struggled to put weight on, and this apparently isn't any different LOL! My midwife says my son and I are very healthy, and there is nothing to be concerned about but I feel like I should try and put some more weight on 😂 Anyone have any tips on how to put some healthy weight on?