Thanks for writing to us.
The unprotected sex you had on 13th with your boyfriend is more likely to cause the pregnancy
that you are carrying. The unprotected sex on 26th is during the comparatively less fertile time of your cycle. DNA test will help in confirmation.
I hope this information has been both informative and helpful for you. You can consult me again directly through my profile URL http://bit.ly/Dr-Rakhi-Tayal