Periods and birth control

Hi guys so I have been on birth control for 6 months now. I started off with sprintec and now I’m using Lupin. Both are generic brands of ortho-tri-cyclen. I take them religiously at the same time every day. (I have sex frequently with my boyfriend and he doesn’t pull out ever.)This month has been odd. When I first started lupin I had spotting for almost 2 weeks then my normal period. The second month my period started on the 2nd placebo day(that period was light and only lasted 5 days) Now this month I had brown spotting 4 days before my period and now an extremely light period that has only gotten slightly heavier each day. I have no pregnancy symptoms so I don’t think I’m pregnant but why is this month super super light all of a sudden? (TMI it’s like a raspberry red color and sometimes pink. I’ve had one clot)