Implantation Bleeding?
Absolutely! Especially if you O'd and were fertilized on day 14 or sooner. Definite possibility! Good luck girl! And I don't know how long your cycles are, but First Response has the 6 day early tests now......not 5, so you may be able to test soon if you have 28 day cycles. http://www.firstresponse.com/earlyPregTest.asp
If you use teh First Response 6 day early one, you could test in 3-4 days and if you're pregnant, you could possibly get a positive result that early. If it's negative, then just wait a few more days and retest. Or you could just wait until you miss your period, but when we were trying with our 2nd baby, I couldn't hardly wait to test! lol