Whats going on?

2 days after Af due (Monday 6th June) i had medium-heavy bleeding for the 1 day and then just spotting for 3 days. Af is normally light to heavy and then light again. This is so out of the ordinary. Tried an hpt 3 days ago on 9th June but was negative. Do you think it was just a 1 off weird Af? Or possibly could be pregnant? Haven't tested again 😕