I don’t know who I’m pregnant by

It could be one of two guys. I got sexually assaulted January 8th. I didn’t say anything about it I just felt ashamed. then my bf and I had sex 10 days later. I haven’t told him I’m pregnant. he’ll think it’s his but I’m not sure if it’s his. I feel like he’ll think I cheated on him since I never said anything to anyone about the assault.