I'm not gaining any weight WTF😩

I'm 15 weeks and I'm still 151 lbs and that's how much I weighted at the beginning of the pregnancy. I'm crying right now is this normal? With my son I gained weight every week, this will be my last child and I hope nothing is wrong with her! I'm so afraid right now! Is this normal to not gain weight in the beginning? I do throw up but not as much as I used to and I do have nausea a lot so I'm so nervous. Ladies is this okay?