I got intimate with my partner on 2nd November and got periods on 5th November (periods were expected to come on 9th November). I am a virgin. There was no penetration and no ejaculation too as he went to ejaculate in washroom. He just rubbed his penis on my vagina for few minutes. So precum possibly could be there. Now I have skipped my periods in December. I took 5 pregnancy tests and all are negative. In don't know what is wrong. I joined a new job in December and also had cold for one week. It's January and still no sign of periods. Is there anything to worry about? Please help.