Is it possible?

Is it possible to just skip a whole period for the month? I'm three weeks dpo, 8 days late for my period and having I guess cramps but they feel like I'm being stabbed in my lower abdomen. There's only a v v v small chance I could be preggo, I just moved back from college, and started conditioning for soccer practice tues/thurs after not doing any physical activity since last August. My period has never ever been this late before, the most has been 3 days late even though it's super sensitive to anything, including the thyroid medication I take. What could be going on? Some days I'm extra worried I could be pregnant other days I'm totally calm and there's no way I could be. Help plsss