I've Had A Constant Nauseated Feeling In The Middle Part

I've had a constant nauseated feeling in the middle part of my stomach for the past 10 days. Lost my appetite too. No pain to speak of, just a sick feeling in my stomach. I do not have a gallbladder, and have always had a cast iron stomach since I had my gallbladder taken out over 35 years ago. I keep getting weaker and weaker, guess it's because I haven't eaten enough food. No pain in my back either.