Could use advice

Had sex (without protection...) on second day of my period, my period is 4 days long, it is day 4 and I still haven’t bled. I beleive I still have time to get the plan B. But I know taking the pill often is bad for your system. My friends relationship they never use protection or worry about pre cum and she’s never taken plan B. I have 3 times already...(I am on birth control but this was during my period when I take sugar pills). Also, he pulled out put a condom on and then came. So I shouldn’t have gotten any in me unless pree stuff.