Paternity advice?

So this is kind of a long story, but I’m hoping to get some advice from you women. So I had my last menstrual cycle May 25th 2019 it lasted for 4 days and ended May 28th 2019. My cycles are usually 35 days apart. Glow predicted me Ovulating on June 14th. Me and my boyfriend had broken up and I ended up sleeping with someone else on May 31st. 2 days after my menstrual cycle had ended. It was unprotected. The next day me and my ex boyfriend unexpectedly got back together. We had unprotected sex almost every day of June. On June 20th I took a clear blue and a $1 pregnancy test and both came back negative. On June 23rd I retested with first response and got 3 very faint positives. On June 25th I tested with the $1 test and got a clear positive. So basically what I’m asking is, what are the chances of me getting pregnant right after my period? My boyfriend knows about the other guy and wants a noninvasive prenatal paternity test done but they are so expensive. If any ladies have had this done and know of a place that is not so expensive please let me know. I am currently 3 months pregnant with a boy. Predicted ovulation window was the 9th through the 15th.