I got intercourse with my partner last month in our own 1st vacation, that was my first time to have an intercourse..
I got worried because my period didn't came at expected date, it should be 1st week of the month.. my period just came last December 31, 2014 until January 3, 2015 and that was a regular flow like last months.. Our last intercourse with my partner is last Decemebr 27, 2014.. Eventually last January 19, 2015 I was wondering because I have spotting period, just a mark under my undies.. should I worry or not... is this normal or not..
Thank you so much..

It sounds normal to me, you had a period after you had intercourse so you're probably not pregnant. Sometimes weird periods and odd spotting happen. Not much you can do about it. If it continues for several months then consult your doctor.

Once you're pregnant your periods stop. Some women experience bleeding throughout pregnancy and mistake it for a period, but you stated that after the sexual encounter you had a regular period. That would indicate that you're not pregnant.