If you can barely move after those first three days, we have some good news...day 4 is a REST DAY! We can't stress the importance of rest days enough. In order to build muscle, your body needs proper rest and recovery.
According to the Cleveland clinic, one of the most common bodybuilding errors is not getting enough rest time for muscles after a workout. So, if you're worried about those gains, give yourself at least one day of rest :)
Enjoy your day off, and try and get at least 8 hours of sleep!