Hello and thanks for your query.
I shall make an effort to provide you with good professional recommendations specific to your questions.
The chances of ovulation during the periods or just after the period is less than 1% if she has a regular cycle of 25-35 days with bleeding for 5-7 days. During the periods, it is the least fertile period of the cycle and the chances of ovulation or conception are practically zero.
But since the duration of cycle cannot be predicted with 100% accuracy, it is better to use a protection. This will prevent any infections also.
As you have said you missed your pills and also had unprotected sex, there is chance of
pregnancy and the bleeding might be
implantation bleeding, so i would suggest you to perform a urine pregnancy test and it is better to use morning sample of urine as it is more sensitive. This is one of the simple and highly accurate method to detect pregnancy.
Yet again, I duly appreciate your query to me, I do hope that you have found something useful to help you and I shall be glad to answer any further apprehensions.
Sincerely,