Need Help.

Ok so if someone else can help me out that would be great. I had sex with a guy on the 29th of april and then had an "unwanted" incident with a different guy on may 7th my periods are very irregular and according to everything it keeps telling me that my conception date was the 7th of may. Does me having irregular periods change that? I'm so confused. I am really wanting to know which one the dad is. either way i will be going solo with this pregnancy i just need to know. If anyone knows anything about this kind of stuff please let me know. thanks  

Have you seen a doctor yet?

yes i have and they say the same thing that they give it like 12 days before they consider u concieving bc of something to do with your periods. idk it makes no sense to me at all. my last period was april 11th and i normally have it one month then skip the next so i dont understand how the normal way they figure things out applies to me. they keep explaining it but i guess i am really not comprehending any of it.

Did they do an ultrasound?

yes they did ive had a couple of unltrasounds done. i found out i was pregnant like may 20th and they said i was almost 6 weeks along.