Stomach pains

So I hear a lot about Braxton hicks and it's hard to know what it is exactly when you feel something going on in your body. I just ate lunch, just a small sub and some chips. I felt full after eating and once I started getting back to work my stomach cramped. It wasn't in my groin or pelvic area tho it was more the left side of my abdomen, and sending pain across my entire stomach. I now feel like throwing up and have an ache in my back. Just alarming because it was painful and iveread Braxton hicks aren't supposed to be painful. Maybe I ate too much or too fast? Any advice would be comforting right now.