I can't walk for long and I can't sit for long either. I'll take a sho…

I can't walk for long and I can't sit for long either. I'll take a short walk and my stomach starts hurting. It tightens up, there's discomfort on both sides of my belly, it pulls down, I think it's from training or maybe it's just something pressing against me, that's putting pressure on me or the muscles are getting strained. ? I come home, lie down, it releases. But lying down all the time is also not good. Has anyone had this happen? Is this normal?