This is new?

I am generally calm in my TWW. I have a predictable cycle, so I don't have to stress too much over my symptoms prior to AF
​Today, I am 5 dpo. And I have this horrible soreness in my lower abdomen, stomach, and lower back. I O'd on 10/05, and was fine. Then, a few days later thought I was getting the flu. On Tuesday I had body aches and low grade fever, but the fever was gone by Wednesday. So I thought it was wierd but happy I didn't have the flu. Then the soreness started. Like if I've been doing stomach work outs... but haven't. 
​It is WAY too early in my cycle to test or (in my opinion) feel any type of soreness in relation to a pregnancy! If I am pregnant, it's early for that sort of thing right? What in the world could be causing this soreness? In my usual cycles, AF symptoms start 4 days before AF is due. I ALWAYS know if she is coming or not. This time, she's not due until the 19th and its way early for AF symptoms for me. And besides that, I've never had this before. In one way I've been blessed with a predictable cycle, but this is throwing me for a loop!