Implantation bleeding V period

How can you clearly tell the difference between a light period and implantation?

My periods are usually on time and they area fairly heavy and I do have really bad cramps and back aches.

3 days before my period was due i had some blood, it started a little red but then was dark brown/red and very light.

The next day was brown and light again, only needed 1 pad for the day maybe 2.

This went on for about 5/6 days and was always brown and VERY light.

I had absolutely no cramps, and it really didn’t feel like I was on my period at all.

but on the 2nd day I had a really sharp nerve pain just off the left side of me which I haven’t experience before and lasted for about 3 hours and that was literally it.

I’ve been doing so much googling and I really haven’t a clue whether this was just a really light period or implantation bleeding.

(me and my boyfriend do have unprotected sex so I know there’s a chance, but i just want some opinions before I spend money on a test)

Also just to add, the past 2/3 days I keep getting headaches, hot flushes and today my nipples occasionally keep feeling like they’re on fire!

Please no negative comments

Thank you x