how old are you? because as women, the older we grow, the more we notice various kinds of changes in our menstrual cycles. Your periods seem quite normal to me, the dates that is. There isnt significant difference. If you are young, ,your body is probably just tuning itself. If you are older, maybe did you change your BCPs if you are on any? if so, that could be a possible factor. Or if you have just started to go on BCPs. Either way, there is nothing to be worried about. I think its perfectly normal. And about your other symptoms, probably stress or other factors. But if you are still not satisfied, why not do a home pregnancy test? Best way to clear your doubts.
If you are pregnant, you wouldn't get your period. Some women think they get their period while they're pregnany, but its not actually a period. That being said, you're probably not pregnant. Have you taken a pregnancy test? That would definitely clear things up for you. Are you ttc?