Cheating on My BF While He Showers the Condom Broke & He Impregnated Me

It was just supposed to be a quick fuck while my boyfriend showered but I'd been eyeing his best friend all night. We didn't mean for the condom to break… but it felt too good to stop. I came hard on his cock, and he creampied me right as my boyfriend walked back in. He pretended not to see… and a few weeks later, I found out I was pregnant. Should I tell him?