Boyfriend is having a baby...with someone else.

So my boyfriend and I have overall been together for 2 years. We love each other very much and know that we are the right match for each Approximately 6 months ago we had a brief break up for about 2 months. He lost his father, and I will not say the reason for our break up. It's irrelevant. During that time, he hooked up with a girl, and she got pregnant. Him and I got back together and after a week of being together she told us she was pregnant. She said she was keeping it no matter what. It's been 6 months since she conceived, and it's for sure his. I want, and have for the most part decided to stay with him, and help raise his kid. Has anyone else been put in this situation? Or have some good advice? It's definitely upsetting, because she is not nice to me. But at the same time it's not the child's fault, and I will love the child like my own. Please help!