Am I overreacting??

Okay so my SO just got this new job. We live a ways away from. His buddy works there too and lives a little closer. 20-25 minutes closer than us. He’s been laid off a while. And gas is so expensive. Well his buddy had offered to fill his truck up but he asked that he stay at his house so he wasn’t wasting too much gas. They will be carpooling. Buddy doesn’t have his own car. This is just until he gets paid his first check. His buddy is a cheater and his girlfriend is also a cheater. That’s how they ( the buddy and the girl) got together. I trust my SO but I’m not sure about the girl. I know as soon as she tries something he’ll put a stop to it. But it’s just the fact of it happening. I don’t want him over there. And I could cry. There really isn’t another option for him. Because I can’t afford to fill his truck up. Idk if it’s my hormones from being pregnant making me feel this upset about it or what. He said he doesn’t want to do this either. But we really don’t have a choice. I asked him to come home if he saw her becoming an issue. And he said of course he would.