Thanks for asking your question at DoctorSpring.com.
Answering your question, even though we can't be 100% sure with respect to the paternity using data, a reasonably good assumption can be reached. For that I'll need few more details.
Before this pregnancy
1. When was your last menstrual period?
2. Were your menstrual periods regular?
3. What was the duration of the cycle?
Kindly reply with the above to help me answer your query further.