Sometimes women can have naturally occuring variations and spotting in their cycles without pregnancy as a factor. There are many factors that can cause those variations such as stress, changes in exercise routines, hormonal variations or even recent illnesses. Based on the information you have given, it is unlikely that you would be pregnant based on that event and the dates, but not impossible. If you miss your cycle on the 1st, take a pregnancy test.
Hope this helps.
My last period was between 12th-20th of jan. Dont kno to be exact. thats just a guess.
You ovulate 2 weeks after your period. It's normal to have cramping and spotting during ovulation.