Are you saying you've "skipped it" as in you just won't bleed during some cycles of placebo pills? Bc that to me implies that even with the hormones, you're periods still aren't normalized.
I had this happen to me in April to be honest with you. I am on a low dose bc, take it just as vigilantly as you, and started off with the breakthru bleeding those first few months and then it was fine. I've been on the pill two years now. Last month about a week before my period was to start I had cramping and then light pinkish bleeding. I needed a mini-pad or else it was staining my underwear, otherwise it was hardly a "period." It turned to brown discharge and continued thru my period pills until I took the first pill of my new pack. Then it stopped. I thought wtf?
I wasn't pregnant though. My next cycle turned out completely normal. I can't explain why some things like this happen. I have thought before that my body was becoming used to the pills and they were becoming less powerful.
I'd wait to see what happens with the placebos but since it's so close to your period pills, I don't think this is unusual. You won't bleed thru the placebos much at all if it's spotting. The good news is you'll know fairly soon if there is concern for pregnancy. I'd call your gyno/doctor after you go thru the placebos if you're concerned with this just to be safe.