So my last couple of periods have been irregular (20/09 - 28/09, 15/10 - 21/10, 15/11 - 19/11, 05/12 - 10/12) but this month, it came on the 20th of January, and is still going.
During December after my period, I have safe sexual intercourse using a condom and my partner said he pre-cumed when he was still in me. When he took it out, I checked that the condom was not broken so it was all clear and safe.
However, I was expecting my period to come around the 5th - 10th of January but It didn't so I took a pregnancy test and it was a negative.
Since the 20th of January, I've gotten brown blood instead of red. It has happened before, long before I had lost my virginity also so I'm confused as whether it is spotting, my period or something else.
It's been 8-9 days and I still have this. It's very very light, and very dark brown. I don't have any cramps whatsoever. Just then when I wiped, I found out that there was white discharge on the tissue but light brown stains around it, technically not a brown discharge.

What do you think? When should I take another pregnancy test?

It was way to early to do pregnancy test, you have to wait till you have missed it for 2 weeks to get a proper test.

Also he will also have some fluid if he is having sex, so yes he had some fluid release.
You can not always see condom failure, they have a 2 to 18 percent failure rate.

This can be many things, from infection, to std, to pregnancy and 100 other possible things.