Congratulations! I agree with the others... check with your doc. When I had my babies, my doctor was an ultra runner. His advice stuck with me, and I've heard it since.... that you can certainly keep doing what you were already doing, but don't start anything new. You, however, are different because it sounds like you started and conceived around the same time!
Don't worry about the weight, either! Just keep us posted and we'll keep you motivated! Best wishes to ya!