Could I be pregnant?

Hi! On the 9th of September I had unprotected sex with my boyfriend. 6 days later I had one day of bleeding - just light. I wasn't due on for another 2 weeks. It's now 4 weeks later. I took a test 2 days ago - negative. But yesterday I had some light spotting for a couple of hours - today it is gone. I'm not due on until the 15th (next week). I've been feeling sick in the last couple of days, slightly bloated but nothing much else to suggest pregnancy. I'm going to wait and see if my October period turns up before trying a final test. Has anyone had anything similar and ended up being pregnant? Thank you x