Weight gain or lack thereof

So as of today I am 20 weeks 2 days. My pre-pregnancy weight was 145 and I’m 5’7” tall, and I was an ultra runner so lots of muscle. In the first trimester I lost 5lbs, and as of today I weigh about 144-145, so gained back the 5lbs I lost. I have my anatomy scan this Thursday, but I’m worried about my lack of weight gain. Anyone else in the same boat? Am I worrying for nothing?