Weight gain vent

Ka

Just a vent I guess. I started off this pregnancy around 120lbs give or take a couple as my weight always fluctuates a little. I’m 5’6 so I was pretty thin. At my three month appointment my doctor told me I was borderline underweight and just to make sure I was consuming enough calories as I was still breastfeeding my first at the time. Fast forward to yesterday, I had my anatomy scan at 21 weeks and I weigh 142lbs. That means I gained 22lbs in a little over two months 😳 I really don’t understand how because I don’t feel like I overeat. I just hope I don’t continue on this pace. I’m also chasing after a very active 18 month old so it’s not like I’m just sitting around all day.