weight management during pregnancy

Hello ladies I had my 16 week appointment yesterday. This is my 2nd time. I got out feeling so sad due to My obg saying I already gained 15pds since my 1st visit. she said I can't gain weight during the next few weeks. I plan on changing my eating habbits and adding an extra hour to my walking. Can anyone recommend any meal plans if you had the same situation? Thank you in advance.