After getting back together with my girlfriend. We found out she was pregnant. [true story] [first time]

My girlfriend and I dated since we were 15 and broke up about 6 months ago. We were both the only people we’d been with at the time but the night we broke up and she slept with her first other guy. We’re now back together but During the 6 months she went through a phase and uhh you could say had a lot of fun. Now we’re back together and at first I was upset but soon realized it was good for her to explore sexually…. But the other day she came home saying she was late for her period. Which wasn’t weird until she never ended up having a period and we took a test… it popped positive and we both knew it wasn’t from me. The crazy thing is she doesn’t exactly know who it’s from either. So I asked her about all the guys she’d been with and she showed me pics… All big black men.. But now that we’re back together and doing good we’re going to stay together and raise a baby together!