Brown Spotting 6 days after IUI and 8 days past Trigger

Lindsey

I had a trigger shot last Monday (8 days ago) and an IUI 6 days ago. 3 days after IUI I had bleeding for a bit and then totally stopped. Now 6 days after IUI I am having light brown spotting. My period is not due for 7 more days. I tested today and have two lines but I'm sure that could be the trigger shot still in my system. Has anyone else experienced this? What is causing this brown spotting?