Disappointment

SORRY FOR SUCH A LONG POST I JUST NEED SOME ADVICE. I’m 10 weeks pregnant with my first baby! I’m not sure exactly how to tell all my family because of the situation I got myself into. I was in a committed relationship with my SO for three years. He went to the military and I stuck by him through everything. Once he got back home he was not the same. He would get anger fast so I decided it was time for us to take a break. We both agreed that we needed to be separated to work on ourselves. In the meantime I started to hangout with friends again and one guy friend in particular. We ended up getting way closer than I thought we would. And we done things back in March. However my SO acted like he was ready to fix things with me so I ended the things with the other dude for my SO. We ended up doing things as well and right afterwards he says he isn’t ready for us to be us again. Which made me sad. Then a few weeks later is when I found out that I was pregnant. Now I’m not to sure who the dad is. Please don’t judge I’ve already beat myself up because I never thought I’d be the one to do that. My SO was the only person I’ve ever been with so it was sudden for the other boy that I didn’t even mean to go do that with. I’m waiting for the ultrasound to see when I conceived because I know the exact dates I did things, but I’m not sure how to explain this to my family. Since I have to wait till the baby is actually born to get a DNA test. Any suggestions. I feel awful. I’m doing this by myself. My SO is still going to be there for me no matter what, but I don’t want him stuck in this because it’s my fault so I’m doing it on my own. I just don’t know how to tell my family this and how to explain to them that my child will have my last name. Sorry for such a long post I just need some advice. I’ve never done something like this and I know they’ll be as disappointed in my as I am myself.