Hello,
Thanks for using doctorspring for posting your query. I have gone through your question in detail and I can understand what you are going through.
Its very very unlikely or say almost impossible for her to become pregnant on day 4 or 5 of her cycle. There was no ovulation immediately after the cycles and hence there is no ovum available. You can be assured about that. To confirm the same she can always get a urine pregnancy test done.
Also next time be careful about the unprotected sex. Along with the risk of pregnancy there is also a risk of sexually transmitted disease and hence one should use condom all the time.
Hope that helps, please feel free to discuss further.
Wish you good health
Regards
Dr. Srikanth Reddy