Morning sickness starting in 2nd trimester?!

Mkmt
I'm 13w4d with identical twins and I was sick maybe three times total during the first trimester although I was exhausted and had terrible headaches. 
Now into week 13, I'm puking like I never did in the first trimester. Yesterday morning, I took prenatals, drank a big glass of water and didn't eat right away and was projectile vomiting. 
I got up early today to eat and still sick. What the hell?