WHO'S THE DADDY!!! HELP

So I'm going to make this short and quick.. Back in March sometime around the beginning I had sex with someone while I was on a break with my boyfriend, my periods are always on and off as I messed up on my pill quite often.. Anyways on the 1st April I got back with my boyfriend, I had 1 day of really heavy bleeding on the 8th April and nothing after. Throughout April I took a few tests to make sure I wasn't pregnant with the March guy and they all said negative. Anyway... On the 6th may I done a pregnancy test and it's came up very very faint. So I took a clear blue and it said 2-3 Weeks. So it's 2-3 weeks from when I conceived which would be around 22nd or 15th April. Am I right? I know the doctors add on 2 weeks because they go by your last period, so if I go back 2 weeks it would be around the 6th or 8th or April. My due date is 13th jan and I'm currently 31+3. Will it be my boyfriends baby pls say I'm right 😢