What if your period isn't late

What if your period isn't late can you get implantation bleeding the day your period is supposed to start? My cycle is irregular so I never know when I'm ovulating I just leave it up to glow to tell me. My period this month wasn't normal. It was on and off the whole time and only had it for 3 days my fertile window was the 5th-10th took a test this morning and it was negative I've been having every symptom but the sore boobs and headaches are the worst..