i had my 3rd a couple months ago..the weight is pretty much off (i gained 26#) but the belly is stretched out still. my regular clothes fit just not as well as id like.
i exercised right up to the end and to get back to exercising i waited 5 weeks. i just enjoyed my baby.
then i started w/ kickbox and light stepping, no more than 30 min.
a month later i am back full-force, actually lifting heavier than ever.
PLEASE give your body time to rest! it is so important and so under-rated.
since you havent exercised in so long perhaps start with just your favorite warmups.
i take it this is your first? you won't be imaxing your first week pp, for sure!
enjoy the rest of your pregnancy and enjoy that sweet baby when it comes!!!