Can't find a time or place to have sex

Alex
My boyfriend and I are having a hard time finding time and places to have sex. We both still live with our parents. We used to have sex at his house while his dad was at work since the rest of his family was out of the country. But they recently got back from their trip so my boyfriend works during the day again and people are always at his house. We've had sex in a park and that was a lot of fun but I'm afraid someone's going to see and call the police if we do that again. And we can't afford to just get hotel rooms for a night. It's starting to get really frustrating for the both of us and we don't know what to do about it