Positive OPK 7DPO but negative at 8DPO???

[Shell77]

I had my IUI last sunday and i triggered with HCG on the friday before.. I tested positive opk till monday ... then negative... But last night I felt like POAS and so I grabbed my digital clearblue opk.. I got a smiley face!! then today i did it and got a negative?? has this happened to anyone? Do you think I ovulated twice? or was it implantation surge? UGH I am so confused!!

[grisandole]

Didn't want to read and not respond. I am not an expert with this so hopefully someone with more knowledge will chime in; but could it be more hormones from the IUI itself?