I have had slight light period for half a day then one two days later all pregnancy test have come back negative could i be pregnant?

Yes, it's possible: You have had a period that is shorter and lighter than usual, lasting only a day. It is possible that this spotting or light bleeding could be from implantation of the embryo. The home test you are using may not be sensitive enough to verify a pregnancy at this early date. I suggest you see a gynecologist to follow up and to have a blood pregnancy test.