What is going on??!

Okay so I'm not actively TCC although it wouldn't be bad if it happened! We bedded on the 1st then I ovulated (I think) on the 5th ish. The last 2 days I've been incredibly tired and have really sore nipples and have mild period like cramps too. Is it even possible that I could be pregnant since I was kinda outside the fertile range (I mean I know it is possible, but is it unlikely?) I have a standard 28 day cycle and I'm not due til about the 19th. I should also add that around when I ovulated I had some (just when I wiped for one day.. Sorry tmi!) brownish discharge which I've never noticed before?
 It's driving me crazy! I just can't shake the feeling that I'm pregnant!
​Any thoughts are helpful! Sorry for the long story!  :) xx