3 BFP but confused about who the father is...

So this is kind of complicated but... I was in a 3 year relationship and in January we broke up. In April, I slept with a guy I had met before. At the end of April I got my period. The guy I slept with doesn’t live in the same country as me, and as soon as he flew back home I got my period. After my period, I slept with my ex boyfriend (the one I was in a relationship with for 3 years) so let’s say end of April and beginning/middle of may I slept with him.

Then, the guy who I had slept with in April and I organized a trip together. We went on the trip at the end of may after I already missed my period that was due the 18th but my period is always irregular cause PCOS so I didn’t think anything of it-just same old. (Ps. When I was leaving town to go on this trip I felt like my boobs were exploding and as if I was getting my period)

I never got my period on the trip, and I had lots of sex with the guy.

So now my question is, I think the father is most likely my ex boyfriend (since after I slept with guy 2 I got my period- and until the end of may I only slept with my ex boyfriend.)

Am I right? I have an ultrasound scheduled but it’s not until Monday and this trying to figure out who it is is eating my brain.

I also had another question: when I slept with guy 2 in April, I got my period 2 days after he left. Is it possible I was already pregnant and it’s his ? It wasn’t light bleeding it was a full on period