Weight gain

Did anyone have trouble with their babies gaining weight in the beginning? So I don’t know what your docs say but mine says they want her to gain a ounce a day. Well she’s 4 weeks old and has only gained 7ounces, that’s like way lower than where they want her....and now I’m freaking out about it. When I called last week they weren’t concerned about her weight, she had gained about 5ozs in a week so that wasn’t to bad, but this week she only gained about 2ozs... I called her doctor today but she wasn’t in so they are suppose to call back Monday. But I’m worried...