Doc,
I'm 19 years old. My last cycle was on 31st Dec and the one before on 3rd Dec. I didn't have intercourse but did take part in some touching things. I took 3 pregnancy tests and they all came negative yesterday and 1 today morning and it came negative. But I still didn't get my period. What is the problem?

Most women have variations in their periods, including skipping a month or being late.
If a penis was not near your vagina, then you aren't pregnant.
You might be worrying yourself too much; stress can delay periods. So can anemia, extreme athletics, and some medical conditions.
But 99% of the reasons are just pregnancy or normal variations.