I'm 17, biologically female (obviously) and I am on the pill but I still get periods. The idea is I skip some periods but I'm supposed to have one every now and again. I don't actually know why but my doctor said it's not healthy to just stop and not have them at all...so I stopped taking my pill because it was time and usually, I get my period after the first two or three days but this time I didn't get one at all. That's never happened before. There was like spotting (I guess?) but it'd been almost a week since I stopped and nothing's happened. No actual full-on bleeding. And I'm not worried about pregnancy because there's an absolute zero chance of that but I'm worried that I'm unhealthy in some other way? I exercise 3-5 times per week and at most 30 minutes each time, which is normal but I think I push myself pretty hard. Especially that abdominal area...would that stop it? I can't really think of anything else except that I'm possibly anemic, I've been extremely tired and pale-looking lately...bruising very easily (I have three unexplained right now) and I cut myself by accident before and the blood was kind of watery. I don't eat a lot of meat, I can't remember the last time I had red meat. But at the same time, I don't try and make up for it with anything else. I don't know if that would stop a period though. Last time I was really anemic (I don't know how to phrase it XD) I got a period but it was less blood than usual and watery like I said with the cuts. Is it bad if I've missed one period? How do you get them back? And do either of the reasons I've listed sound plausible or do I need to see a doctor?
If this is the first time you have missed one then I would keep going until the end of the next pack and do the free week again and see if it happens again. I take two or three packs in a row fine. If it happens again then I would see your doctor just to be on the safe side.
If you think you might be anemic you should try taking an iron supplement for a while to see if that helps. If you don't eat red meat you could probably use it anyway. I don't think it's a huge concern if you miss a period while you're taking birth control, but with the other things you said are going on you might want to see a doctor if it doesn't clear up soon.
If you are really pushing yourself hard when you work out, then your periods could stop. If you keep missing your period, you should definitely get it checked out. But sometimes the human body is just weird and does things for no reason. Just keep watch for anything concerning, such as feeling constantly fatigued or missing over three cycles in a row.