My period came on Tuesday and lasted till Friday/Saturday. Although it wasn't a normal period it was very light pink and brown. It was only there when I went to the toilet and wiped. Throughout it I got a lower back pain and stomach cramps. I had unprotected sex a couple weeks before it. I took a pregnancy test a Couple days ago an it came up negative but could I still be pregnant? I've never had a period like that before

Just wait and you will have more than that one... EVERY woman will have irregular periods from time to time in the roughly 40 years they will have them.

You have to wait until you are at least 2 weeks late for a period or you will likely get a negative that doesn't mean anything. (you can be pregnant and if you test too soon it will still show a negative).

I haven't kept track of my periods recently but I knew it was due. It wasn't like a period though, it lasted from Tuesday till about Saturday and I didn't need to wear a pad or tampon it was only when I went to the toilet and wiped it was a light pink colour and brownish on the tissue. I also got really bad cramps and lower back pain which I never get with a period. So I was wondering if maybe this was implantation bleeding?

Many professionals in the field do not believe implantation beeding is real.

The egg is microscopic... so why would it cause bleeding.

Women sometimes have unexpected spotting between periods,. maybe that's all you had. If you are pregnant you won't have your next period... figure 2 or more weeks after when you guess it would be due... (because doing it too soon might give a false negtive). And take a HPT when you wake up, the first time you pee.

Implantation occurs in a lot of woman from the research I've done. But I will take test soon anyway.

Implantation occurs in a lot of woman from the research I've done. But I will take test soon anyways.

You got that off the internet I assume... I got this from actual Medical professionals in the Obstetrics field, one of which is a moderator on this site.