Baby won't go into deep sleep!

Hi! My husband and I are completely out of ideas and now our relationship is starting to suffer.

We have an 8 week old boy, he is breastfed. During the night time he won't go to sleep and stay asleep. He'll pass out grunting, fall asleep for 10 minutes, wake up and start the entire thing over again. In 8 weeks we've maybe had him sleep longer then a 4 hour strech three times. Naps we can get