Weight grain?! 😳

Samantha
I'm 19 weeks today when I first found out I was pregrant I was 169  now I'm only weight 158 I'm not gaining any thing. At the beging I was super sick so my doctor gave medicine for it now I'm ok. 
He also said I should be gain back. I want to gain weight to be on the safe side. Is this normal ok?? Â