Boyfriend always leaving after sex

Katie🐠 • Pro-choice. 6-24-14
Me and my boyfriend have been dating for close to a year now and in the beginning we would have sex and he'd always stay with me right after. Then months later I got pregnant. (Not planned) he started working a lot recently.  I went on vacation for over a week without him  I came back today. And he didn't even spend the whole day with me. He kept talking about how he had to go. We had sex then he left right after. This isn't just a "sometimes" thing. it feels like he always has to go or do something and doesn't even cuddle after sex anyway. I know he loves me and cares about me. I don't know why he always has to leave right after sex. I'm so confused and starting to get hurt over it. Any advice?