Is it ever possible to get a flat stomach again after a bikini line hysterectomy?

I had a traditional bikini line hysterectomy 3 years ago after a cancer scare. I always had a fairly flat stomach, not ripped and firm, but flat-ish. 3 years later, it seems the more I try to get my stomach down with diet and exercise, the more intent it seems to be on staying put. I am not on any type of hormone therapy, nor am I on any type of meds for anything at all. Is there a reason why my weight loss is stalled and my stomach is stayin put?