hi, i am 18, had unprotected sex on 24/12, and my 2nd last period was on 26/11. my usual length of period is 36-40 days, and then i got my period after sex on 1/1. i also got to a gp and took prostinor 2 within 24 hous. the period on 1/1 was more of brownish on the first day as compared to the previous times, but the 2nd days and after was fine and was a little less compared to previous times though it also spanned through 3-5 days. am i safe or will i have a high chance of pregnancy?