late implantation bleeding??

My cycles have been pretty irregular for a year now after I've had my first baby. my period once was as regular as can be, every 28 or 29 days. now it's been like every 34-40 days 😒 I only know that bc when I was using the flo period tracker app I was always really late for my period and it would scare me into thinking I was pregnant every month so I deleted it 2 months ago and then found this app a few days ago. I really have no idea when I had my period last, but I do know that I had sex 3 weeks ago and we used the pull out method. I feel like I've been pmsing for a little over a week now and today for the first time ever I got some sticky discharge with brown in it. normally my period would just smack me right in the face full on.. or at least a lotttt more than what I got today. wtf man, any ideas? I'm sick of thinking I'm pregnant every month but this has never happened before