If you're 8w5d right now it was the second guy. You'd be closer to 11-12 weeks if it was the first guy.
Well if you bleeding from the 11-15 was not heavy and had clots i dought i was a miscarriage. If i had to guess id say its the first guy but get a test to be sure.
well....the only thing you can do is get a paternity test once the baby is born. u/s can be off by up to 2 weeks. be sure to inform both men. let them know that you will be getting a paternity test once the child is here.
good luck.