Cycle day 37 negative test due to magnesium?

[Chaiilatte]

i was wondering if anyone could help me as I'm in a panic. I'm on day 37 of my cycle with no period yet. I've had 2 negative tests (I'm not trying to conceive but I didn't know where else to post this) I was taking magnesium glycinate quite a bit in December due to migraines. Can this delay my period? Has anyone experienced this?
I had unprotected sex December 29th. Although he didn't finish inside me and was only in for a couple of minutes, I know there would still be a chance of being pregnant through that. I'm just really hoping it's the magnesium glycinate seeing as I've had negative tests.

im aware I've been stupid using no contraception when I do not wish to be pregnant and it will not be happening again so please don't give me grilling. I feel shit enough.

Do you take any hair and nail supplements that contain biotin? They can affect pregnancy test results.
Magnesium doesn’t affect cycle length afaia.

I take a multivitamin. I've just had a look it's 100ug biotin. I've taken a clear blue digital again this afternoon and it says not pregnant.

I haven't taken the multivitamin for over 48 hrs though so I'm assuming I should be ok? And the negative is accurate?

A quick Google says 72 hours for most people, it doesn’t say how long for the minority.

In most patients, biotin is effectively cleared from the system within 72 hours, depending upon the dose and time of ingestion, and will not interfere with test results after this time.

more info, but just saying safe daily dose is 30mcg & that biotin may stop a line appearing on a hpt. Your 100 international units is just 2.5mcg so I’m not sure if that would make a difference tbh.
https://utswmed.org/medblog/biotin-risks-postpartum-hair-loss/

Thank you for the information. Taken another clear blue this morning with the first wee of the day and it's negative again but still no period (cycle day 38) 🤷🏻‍♀️