A.M.
I get my sanity at the gym! My son goes to their kids club childcare room there, while I workout, clear my head and if there's time - swim in the pool, hang out in the dry sauna or hot tub. Love it!
LA Fitness has month-to-month memberships for $30/month - no long-term contracts. And they have GREAT classes: yoga, pilates, step aerobics (love this!); kickboxing; weight/strength training class, cycling, etc.
Also, don't know where you live... but being active in a MOPS (Mothers of Preschoolers; www.mops.org) like group is helpful. You get hear advice/support from other moms.
My church offers MOMS Connection (similar to MOPs) ... let me know if you live near Plano and would like more info about MOMS Connection.