Missed period

So iv missed my period and have a brownish discharge I’m also on the pill and taken the morning after just incase also took a pregnancy test and it was negative

I have been under a lot of stress lately and I’m sick with some kind of stomach bug or something which I’m seeing a gastro dr

Should I take another test to be sure or would this be from all of the above? And had anyone else experienced this? My anxiety is through the roof atm as I don’t want to be pregnant lol