How to gain weight while pregnant

Okay so I had my 20 week appointment a couple days ago . Baby is 12 ounces so far. Everything appears to be good . They didn’t mention anything but she was already head down . Since I’ve been pregnant I’ve only gained 1 pound ...😐

What can I do to gain weight . My doctor said she isn’t too concerned but I’ll need to gain 14 more pounds before the end . Apparently I’m small because everyone is shocked that I’m pregnant cause I’m not noticeably showing that much.