Weight gain

I know this has probably been brought up already but i am 5'7 and a slender/athletic build. I just turned 19 weeks and am already up 19.5 lbs. i was trying to gain some weight before becoming pregnant but conceived when I was about 4 lbs away from my goal.. So based on that number I'm up about 15 lbs.  am I gaining too fast? My doc said I could gain 35-40 lbs for the whole pregnancy but I don't want to hit it too fast! I lead a pretty healthy lifestyle although my workouts have lost some intensity. I obviously don't want to lose weight, but just wondering if the rate is gaining is okay?! I'm totally fine with gaining but want to be healthy! I see my doc next Monday.