Sooo hurt cant stop crying

so during a break up, he had a break baby ????. We got back together literally right after she got pregnant I guess because we have been back together for 1yr and a month and she has a 5 month old?, its the first Christmas ever having to share him. Idk how to feel or what to do. He went to drop off gifts for the other child. And will be back after but it still just feels sooo crazy. Any words would be ok