I know everyone gains weight differently during pregnancy, but by mid-second trimester were you gaining a pound a week?

I continue to be a little concerned of my weight gain (or lack thereof). At 20.5 weeks, I'm up 7 lbs from my pre-pregnancy weight. Overall, I think that's not bad, but the pace of my gain is odd. I gained 3 lbs in the first 10 weeks, and then nothing for six weeks....but gained another pound during week 16. Then I pigged out like crazy during the holidays and gained 4 more pounds by 19 weeks. At the gym last night, I had lost a pound so my total gain is still 7 lbs.

My midwife wants me to gain 25 lbs - I could obviously still get there with 19.5 weeks to go, but I pretty much need to gain a pound a week, which isn't happening yet. I was hoping to be up 10 lbs by 22 weeks, but that means I have to gain 3 pounds in the next week and a half, which probably isn't healthy. I really do eat quite a bit so not sure why I'm holding steady. I work out about 4 times a week, but nothing crazy (usually elliptical or a walk/jog combo for 30 minutes). I know your body gains what it needs to gain, but I want to make sure our baby boy is growing strong! My belly is growing pretty steadily, so I know that's a good sign.

(FWIW, I'm 5'2 and pre-pregnancy weighed 110 lbs).

What has your experience been with this?