Weight gain question ???

Erin • Second baby boy due July 9th, married !
I'm 22 weeks pregnant with my second baby. I didn't gain any weight my first trimester actually I didn't gain anything till about 19w. Now I'm up 9lbs In 4 weeks ?? Is that normal ? I feel like I haven't changed my eating habits and I can just look at food and gain weight. I hope it doesn't keep up at this rate. Don't really know what to think. Thanks for any input.