Spotting before AF

Anyone out there have experience with brown spotting happening anywhere from 2-4 days before AF starts? I’ve been ttc for going on 6 months now and every cycle I get brown spotting before my period starts. This occurs anywhere from 10-12 DPO. I’ve read that I should consider the first day I see spotting as day 1 of a new cycle if my flow starts to get heavier, which it does for another 3-4 days. Is this considered a short luteal phase? I’ve been off of the pill since February 2021 and actively ttc since May. I’m 29 years old. I’m also going for my annual OB exam in November so I plan on asking then as well. Thanks everyone!!!