You are rather vague about the date(s) you cheated on your partner. There is a lot of difference between the start and the middle of October! Can you supply
- the cheating date(s)?
- the date your last period started?
- the length of your cycle (typically 28 days)?
- the date your following period was expected to start?
- the date the baby is due?
If you love him so much, why did you cheat on him? Why was it "unfortunately"?
If your period were indeed due 24 Oct, then sex before 18 Oct would not likely be a fertile time. However, if you have a typical 28-day cycle, then Ovulation on 24 Oct would suggest your previous period started about 10 Oct. Then the beginning Oct would probably be before your Oct period. So the information is rather unclear.
It is difficult to be certain, particularly when you don't know the dates. How did you use the online calculators if you did not know any of the data I requested? Do you really have no date for the baby's birth?
As I said in my first response, if you had a period after you cheated, then it is very likely that he is not the father because normally you wouldn't have a period when you are pregnant. Was it a normal period?
However, some people do have periods during, and even throughout, their pregnancies. Without any data being available, then only a paternity test would give you the answer.
Can you not answer any of the 5 questions I posed?
I have just noticed another post of yours where you do give the baby's due date (answering my question #5)!
If the due date is indeed 17th July 2015, then the father would not be anyone you had sex with in the first half of October, or earlier.