Wth. IB?

OK so I've never been one to get SUPER paranoid in my TWW. Honestly, I'm usually just doubtful that I'm pregnant. My cycles have been super irregular the past 7 months (since coming off bcp) my last one being 100 days exactly. I only started with help of the medication Provera. Glow says I should start today. Today would be a 30 day cycle. I have no idea when I ovulated. I wasn't getting a positive opk at 20 weeks so I figured I missed it or I wasn't going to ovulate this cycle. I honestly thought it was the later bc that just seems to be the way this ttc journey is going. Like of course, now that I got my cycle after 100 days, I'm not gonna ovulate. So, anyway I pretty much gave up testing around CD 20. Well Monday night (this would be CD 28) before I got in the shower I had a little spotting (teeny tiny- red streak in CM) everytime I wiped. Then I got in the shower and checked my cervix low firm and either med or closed (still learning) and a little more pink tinged CM. Also that day my back was killing me but I was doing a bunch of heavy duty cleaning. So, while in the shower I just assumed and accepted the fact I was about to start. I haven't spotted SINCE which is weird for me. I usually don't ever "spot" . Also the past 2 days I have been very thirsty especially during the night which is when it feels like there is a big piece of cotton stuck in the back of my throat. I'm just wondering if its possible it was implantation bleeding. And when I should test. Dr said if I didn't start by day 32 with bfn to go ahead and start Provera but since Idk when or if I ovulated, when would you ladies test?I tested Mon morning before the spotting and it was negative. Ugh. So many questions! Sorry. Anybody with a similar story of IB or dry mouth, that got their bfp?