8 days old & constipated

Grace • Zion James 1/22/17, Kingston👼🏽 10/14/18, rainbow baby due December 19’🌈💕
My son hasn't pooped for his last three feedings, and he was pooping within 20 minutes of eating before. You can tell he's trying cause you can see hes pushing, and his Little face gets all red. Also he's REALLY gassy. What can I do to help him out? I've been by cycling his legs because I read that helps but I don't know what else to do