No weight gain.. no bump..?

So, I’m 20w+1d, and I literally haven’t gained a pound.. I had morning sickness in the first trimester to where I lost a couple of pounds, so I’m technically lighter now than what I was before pregnancy. However, I’ve been eating like never before and haven’t gained a pound! Other women have gained at least a pound or two.. so it kinda worries me. I also barely have a bump.. in the morning there’s nothing and then if I eat I get a little something and then it repeats.. I’m just a ftm needing some reassurance I believe. I have my anatomy scan on Tuesday, so I should have baby’s measurements then. But all our other appointments doctors say she’s doing good.

Any advice?

I also have IBS, which my doctors are aware about.. but I haven’t had many flare ups since I got pregnancy (I’ve been able to actually enjoy ice cream sometimes, lol). Idk If that makes a difference.. but yea!