positive and then negative tests ?

I had a D&C done January 18th. bled in and off for two weeks. i stopped the 31st. had definite signs of ovulation february 4th. we did the deed. i took a pregnancy test (first response) two days ago due to nausea and it came back faintly positive. took another one last night and same thing , bought a different brand and took one this evening and it’s completely negative.

could the other two just be due to leftover hcg that somehow made it out of my system in the last 3 days ? or could this be a new pregnancy but extremely early