Thanks for query,
It is natural that during pregnancy
one gains weight due to more rest and having nourishing diet etc but in your case weight increase is much more.
Now observe strict diet control with restriction of fat and carbohydrate
As you are lactating mother you should not deficient in nourishing food.
Avoid fried,junk food and ice creams,pudding.
Go for light exercise like walking,swimming,abdominal exercise
Avoid taking more tea,coffee.
Ok and bye.