Hi! I am definitely not an expert, but I thought I'd send you some Hugs! Does he have a prop that he is dependent on? Is he hungry? Are there developmental things interrupting his sleep (rolling? teething?) What is his daily routine? He should be on a 4 hour EASY at his age.
Infant's sleep cycles are about 45 minutes long so there is something preventing him being able to put himself back to sleep as he transitions from one cycle to the next.
Good luck!