There are a few threads going about weight gain/ check ins/ ect. You might scroll just a bit and that will give you a comparison. Really as long as your doctor isn't concerned you're probably fine.
This is posted here on the first page. Your doctor will tell you if they're concerned, but you'll find a lot of people here that have lost weight or not gained.
I have had a similar situation. I'm a teacher so I feel like I'm running around all day, and I try to workout regularly. I've gained 3ish pounds. My doctor said not to worry and that some people will make up for it later - eek! I'm hoping I'm just on a really slow steady gain to 20 lbs or so.
If your doctor has not expressed any concern about weight thus far, then don't worry about it. Be happy you haven't gained anything but like another PP said, the weight can be made up later.
Re: Little to no weight gain 20 weeks
https://forums.thebump.com/discussion/12627599/weight-check#latest
If your doctor isn't concerned, I wouldn't be.