Implantation bleeding

How long after implantation bleeding can a pregnancy test show positive? I have PCOS and my cycles are very irregular but had been getting better with recent weight loss. My most recent cycles were 42 days, then 38 days, and most recently 36 days. However, I'm currently on day 53 of my current cycle. I noticed slight spotting on Tuesday but nothing more. I'm 31 y/o and TTC my 2nd child for 3 years. I took a test a week ago and it was a BFN. If it was in fact implantation bleeding, how long do I need to wait before testing again?