I'd gained about 2ib too at 21/22 weeks I'm now 29 and gained 10ib. So its normal don't worry, I was 8st 6 pre preg and 5'6. With my last I only gained 4ib at full term from my pre pregnancy weight cause I'd been so ill for first 5 months, he was born totally healthy and 9ib. I think aslong as your eating good etc then its not a huge concern I find I gain the most in my last trimester ds1 I gained 4st, so all mine have been completey different xx
Not uncommon to gain very little weight and even lose it in the first half of the pregnancy. I had low appetite throughout much of it, and lost weight at first. Didn't regain my pre-pregnancy weight until about 18 weeks. At 22 weeks I reckon I'd put on about half a stone. But I'm bigger than you- five three and size 14 with big hips and shoulders and biggish boobs. And I did most of my growing between 20 and 30 weeks, and had massive amounts of water. Some people don't balloon til later on.
I have put on about 8lb now (29 weeks tomorrow), but it has only happened quite recently. I have quite a big bump now and at a scan just before 28 weeks they estimated the baby weighed 1.1kg and all measurements were fine.
If your Midwife was not worried and everything was good at your scan try not to worry. You may just start to gain in the last trimester.