Barely any weight gain- worried

Sarah • 💙Leo-4.13.16 🌈Landon-6.23.18

So I'm exactly 19 weeks today (yay!) and had an appointment with my OB. Throughout the pregnancy I've only gained 4 pounds. That's it! But I've got a small bump, and the heartbeat sounds great. So I'm worried that at our 20 week ultrasound we'll hear something is wrong ☹️

With my first pregnancy I gained a lot of weight and I had my son at 38 weeks and he was 7lbs 15oz and perfectly healthy! I'll be devastated if something bad happens to this one or if he'll have a low birth weight- I won't know what to do 😣

My doctor accused me of not eating enough, but I'm eating small meals every 3-4 hours like she told me to AND I snack. I'm not sure what else to do 🤦🏼‍♀️ Has anyone else had this happen?? Barely gain any weight? Did it all catch up third trimester?

Here's a pic of the bump- I'm still in shock that I've only gained 4lbs