I had sex with a friend it was unprotected but he didn't ejaculate inside me ( I finished him off by giving him a hand job so he didn't even come close to coming inside me). 2 days later I then got my period as expected. I usually have a regular 28/29 day cycle.About 2 weeks later (14 days from the start of my period) I then slept with my ex boyfriend (who did inside me)... 11 days after the deed, I got paranoid that I could be pregnant so took a test off eBay (those cheap early detect ones) however it was negative.. . I missed my period (17 days after sex) took another test and it was positive. I have had my 12 week scan and the date baby is 12 weeks 3 days.. but I counted that back (took off the 2 weeks they add on) and 12 weeks 3 days was 1 day before I had sex with my ex boyfriend so either the baby is big or the scan is a day or so off.

I am now worrying that it was my friend who got me pregnant (although I had a period and negative test after... test would have been about 26 days after we had sex aswell). My mind thinking all sorts like the eBay test was wrong because it was cheap and that I could have got pregnant by pre ***... also I am now thinking that the dating scan could be almost 2 weeks off and my friend could be the dad?
I think I know that common sense tells me my ex is the dad... I would just like a few more opinions on this. Hope it all makes sense. What do you think. Thank you so much I am going crazy

Either person is possible. Scans aren't exact, they're a best guess and can be off by 2 weeks or more either way. In other words, you won't determine paternity based on a scan.

Judging by what you posted, your only option is a DNA test after the baby is born, to determine paternity.

Good luck.