2 months post op with ventral hernia exercise ideas needed

Hey all, today is my 2 month surgiversary and I've been doing walking so far but really want to work on strength, (specifically core strength). Last week I tried following a Jillian Michaels workout video that was all strength based (for the first time in who knows how long) and somehow gave myself a ventral hernia, in my belly button area. I'm already scheduled to go in for repair the end of September but I'm wondering if it's OK to do core exercises in the mean time, and if so, what type of exercises can I do without making the hernia worse?