Okay so I had intercourse in early August(protected and unprotected, but he didn't ejaculate in me the unprotected time). And had a period September 3-10(a little heavier and longer than my normal 3-4 day one). I haven't had my period in October, November, and am late for my December one, and by the looks of it there's no sign that one is coming this month either. From October-November, I had symptoms which could quality as PMS or pregnancy symptoms..head ache, really bad abdominal pain, lower back pain to name a few. And I still have occasional stomach cramps this month as well, but that's the only symptom I have left. I took 3 home pregnancy tests in the span of the three months and all were negative so I marked out pregnancy. And I looked up reasons why it could be late, like stress, which definitely isn't the problem, and the only change in my diet is that I am eating mean again, but that happened before my period in September. I mean I am overweight, but definitely not obese by any means. I looked up different kinds of cysts and so far that's the only logical explanation I could find(I will go to the doctor about it in January). So why would my period be late?