Isn't yoga grand?! I practice an hour of yoga (morning) and an hour of Pilate's (evening) each day, seven days a week. You will be AMAZED at how quick you gain massive amounts of core strength.
When I first started practicing my core was *so* weak it wasn't even funny. Especially with Pilate's I thought I would throw up my core was burning so bad! I bet in a few weeks time your core will strengthen more than you ever thought possible.