<<The pain was never only to the left side, it was more all over and then it ended up going away in the center.>>
Gall Bladder.
You are probably one of those dieters that decided oils and fats are bad for you. Unfortunately they are very necessary to prevent a whole chain reaction of problems in your guts.
Let me guess, you get funny colors in your turds, have regular constipation, greasy foods cause indigestion, and you get diahrea alot. The pain begins in your left side because of stimualtion in the nerve plexus that connects your internal organs. The pain normally subsides upwards into the top of your sternum or to the middle of your sternum. The discolored turds is the lack of bile in your digestive tract. (Bile is required to digest fats.) The bile isn't coming out because your gall bladder is stuffed full of clay globules called "gallstones". The lack of bile often causes your large intestine discomfort because the food is only partially digested when it gets to that point. The constipation is because your food is too dry. The diahrea is because you get constipated. Constipation actually makes bacteria grow out of control in your gut causing further health problems. Oh, what a dreadful cycle.
Instant relief is to take down a cup of light oil and a couple of teaspoons of epson salts. It tastes horrible, but works. You'll poop your guts out for two hours but the pain goes away instantly. Introduce oils back into your diet and it helps alot, too. Been there, done that. 🙁 Ever since I put oil back in the diet its never been a problem since.