It is possible you ovulated a little earlier than you thought, but it takes 6-10 days for the egg to implant and only then do your hormone levels start to go up, which is what causes a lot of the symptoms you mentioned. After you ovulate there is a natural surge in progesterone whether you are pregnant or not, which could have some physical effects. I admit what you describe sounds right on for being pregnant, but if you've been reading about these symptoms it could have gone to your head too. Unfortunately you really just have to wait until the first day of your missed period when you take a test. There are so many factors at work in our amazing bodies whether we are pregnant or not that you could read into anything until then. In the meantime just take extra good care of yourself. Good luck!
Too early to say. Implantation doesn't occur after three days, and you won't feel symptoms related to pregnancy until it does. Generally implantation will occur after 6-14 days. You can take a pregnancy test in two weeks with first morning urine.