Normally the fertile days are around ovulation which usually occurs 14 days before the first day of your period. In general, the fertile period in a cycle starts from the number of day calculated by shortest cycle minus 18 days and ends on the number of day calculated by longest cycle minus 11 days. So, if your shortest cycle is 28 days and longest is 35 days, your fertile days in a cycle can vary from (28-18) = 10th day to (35-11) = 24th day, where first day of your cycle is the first day of your period.
As of today, you would be on the x day of your cycle, where x=length of your last cycle+5 days. Assuming the length of your last cycle as 5 days, it may be the 10th day of your cycle, which brings you to the first day of fertile period assuming your shortest cycle to be 28 days.
Now, even if your boyfriend did not ejaculate, there is a chance to semen being present in the prostatic fluid which is secreted before the semen.
If you do not wish to get pregnant, you can try emergency contraception
which is available over the counter in the market (levonorgestrel
0.75 2 doses 12 hours apart, where 1st dose should be taken within first 72 hours of unprotected sex). However, this should not become a routine practice as it disturbs the regular cycles. Please don't consider this a prescription. The information is for general awareness. I would recommend you to visit a OBGYN
for further evaluation.
Hope that helps.
Take care and be well.