How soon to test positive

I have very consistent period and Today should be the start of my menses but I have spotting since yesterday. It's not enough to fill a pantyliner for the past 24 hours. I did my IUI on the 10th this mth, should I already been tested positive if it's successful? 2 days ago I tested via pregnancy kit, but result only hav 1 line. Still have chance to be pregnant? Should I do another test tomorrow morning? Anyone had similar experiences before? The tww is torturing :(