I need advice ASAP

I am a teenager therefore my period cycles are usually irregular. I get my period late all the time. And my period usually last me 6-7 days and is really heavy. I had unprotected sex on the 24th of November, about a week after my last period ended. 4 weeks after my last period, I got what I think is my period, it was lighter than my usual period would be, however I researched and it seems like it was too heavy to be just implantation spotting. It also lasted 6 days so I was sure it was my period but I took a pregnancy test just incase to make sure. The test came out negative so I was ok. It’s been over a month since that period and I’m waiting for my period and I’m a week late and my periods always late but I’ve never skipped a period so did I possibly take the pregnancy test too early for it to be accurate? I took it almost 4 weeks after I had sex and 5 weeks after my last period.