Slow and steady wins the race..........90 pounds in 3 months I agree is very unhealthy for you. Losing weight that quickly can cause you to gain the weight back and some very quickly.
I am not trying to discourage you, however, you need to take care of yourself first. You should not lose more than 2-3 pounds a week, and according to my calculations would take you 7-8 months tops with a sensible diet. (fruits, veggies, fiber, healthy proteins and healthy carbs) and a little excercise

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I hate excercising myself, so just find things you enjoy to keep your body moving and the pounds will just melt away.
8 months is not a long time......considering how long we have all been TTC. I wish you luck and tons of baby.
I know you can do it.
