Copper coil & late/missed periods

[acatcalledjohn]

Hello MNers!

There seems very little clear info online re missed/late periods on the copper coil. I had mine fitted around early-mid May. First period started 15th of June. Since then the number of days between periods seems to be settling/levelling (35, 27, 32, 29). However, I am now 9 days late (based on a 29 day average over the last three months). I have had some minor cramping in the last few days, and only today some very mild brownish discharge, but that's about it. Two days ago I did a pregnancy test as we have had sex around my supposed ovulation dates, but the test was a firm negative (though done around 6pm which I know is not the best time).

My questions are:

Are missed/late periods on the copper coil common?
Would an ectopic pregancy increase the chances of a negative result on a pregancy test?

Update: I appear to have started AF today - mostly old blood and some red this morning, which is not quite how it would be normally, but so be it. That makes my last cycle 39 days though. Did do a PGT this morning (I wiped but nothing on paper, POAS, then wiped as normal and hey presto, blood), though that was another BFN.

My coil seems to have made my cycle shorter although whether that's just because my periods are longer I'm not sure. Definitely altered them though

Yeah, mine are altered too, but being quite this late is just odd. This doesn't seem like AF (unlike I thought early Monday) as I'm only suffering some spotting, leaving me worried that I might be PG and simply suffering from implantation bleeding. I can't find any info re AF simply being late or skipped on the copper IUD.

Thing is, PG wouldn't be good as DP suffers from anxiety & depression and would have a full blown mental breakdown.