It could have just been from ovulation. I normally get some spotting like that for a day or two right before ovulation. It is common and just is a sign of the egg releasing from the ovary. Have you had unprotected sex since then or around then? Unfortunatly the only thing you can do is wait to see if she shows up. You could also take an early response test but I wouldn't take it until like 2 days before your missed period. Good luck and I hope you get the answer you want soon.
There is a chance that the discharge you had could be implantation bleeding. Like Alaysha said, the best thing you could do is wait till your period is due, and if it doesn't come or is lighter than usual, try taking a HPT with first morning urine.
Well if you had unprotected sex than there is always a chance of pregnancy. Unfortunently spotting could be caused by a million other things not even related to pregnancy. Stress being one of them. Only thing you can really do is wait until you actually miss your period and test.