when should I start gaining any weight?

here's a ball park range of how much gain to expect

I gained 18 freaking pounds in my first trimester, and I was diagnosed with hyperemesis and I threw up 95 percent of the day. Everyone is different.

Normally 2nd and 3rd trimester but everybody is different

that's up to you and your OB I'm 31 and still down 24lbs and not gaining

Well I'm 22 weeks and never gain any yet