Implantation bleeding

This might sound like a stupid question, but I bleed yesterday morning, just a little bit in my knickers- brownish colour- nothing major really after that at all. We had sex on Saturday. I want it to be implantation bleeding. I have irregular periods, and only finished it just over a week ago. What I'm wondering is- can ovulation be that early if u have irregular periods? Been trying for 6 months now- but always worried I can't because of irregular periods. Thank u