I've always really struggled with my weight, and put on over 6 stone in my last pregnancy
I definitely took 'eating for two' in a very literal way, and used it as an excuse to be a total pig [ashamed]
I managed to lose the weight afterwards (and a bit more besides), but it was a long hard slog if I'm honest.
This time is very different, as I've put on less than half a stone at 21+5. I'm just being careful and was walking lots (but now have SPD so am definitely doing much less than I was a few weeks ago).
The weight gain from last time is one of the reasons I will have a 6 year age gap between my dcs - I was terrified of getting pregnant and stacking it all on again. All your 2 stone gains sound perfectly normal and reasonable to me, so try not to worry 
I also had PND last time, and will be straight to the doctor at the first sign of any trouble.
Lovely to hear more good scan news today! The spreadsheet is so unbalanced re. boys/girls, surely all remaining scanners must be having girls to even it out?!?