Three weeks late on copper coil...?

[earlgreysandpuppies]

NO idea what topic to put this in. Apologies if misguided.

So I'm around 20 days late for my period, which I think is the latest I've ever been. My periods are pretty irregular and always have been but never been more than 14 days late. I've been regular for the first time in my LIFE for the past two months and got really excited to finally be normal and predictable in my cycle and now I'm three bloody weeks late I took a super cheapy preg test around a week ago (would have been around 2 weeks late) and it was negative.
I've been really stressed lately but I've started to have brownish discharge in the past couple of days but I don't feel at all like I'm gonna come on and ALSO I should probably mention I'm on the copper IUD which has made my period a lot heavier and longer so I'm really confused.

Does anyone have similar experience?
Do I go to the docs or am I wasting their time? Thanks