Weird feeling

I had unprotected sex 11/8, had a 1 day full period with very scant bleeding only there when I wipe 3 days following. From the 21st-24th of November. December 1st I started this very scant bleeding again and only there when I wipe with some mild cramping and back pain. Today December 3 I took a pregnancy test it was negative. Should I wait and take another test? Because at this time it would be barely 4 weeks after conception? I'm not completely sure how implantation works, but l've read some girls don't get a positive until way later. What do we think?