mass in my abdomen

Help! Has anybody ever had or heard of this? I had a tiny dime sized spot on my incision line about 18 months ago - my surgeon said it was a hernia. I got pregnant so had to delay any repair. After getting pregnant and delivering, I had some pain and then I felt a "pop" and it became HUGE - about 6x6 and is painful. You can really feel it on the abdominal wall. I had a CAT scan and now I'm having a MRI tromorrow. I'm hoping it's a hematoma, but I'm pretty freaked out. Anyone familiar with this?