Hi Kourtney, I had the exact same symptoms as you. I thought it was PMS. I tested last week and got a BFN. I thought for sure I would have a positive by then if I was pregnant but it was too early, even though I had missed my period by several weeks. I just got back from the Dr's office and they confirmed that I am pregnant. If you ovulated later than expected, it is possible to get a false negative. So, all that being said, I would keep testing once a week until your period starts or you can make it to the Dr's office. Good Luck!
you should definitly take a test, u can test one day after ur first missed period so its not too early to test. and yes u can get very emotional in early pregnancy, all them hormones racin all over the place ur up one minute and down the next. hope u get good news.
about the runnin, i think as long as you always ran and arent just takin it up it should be fine, u might just want to run it by ur doctor to be extra sure.