Will not nap!

Claire
My LO will be 8 weeks tomorrow.  The last week or so he will go down for his naps but will only sleep for 30-45 min.  He use to do great and at least sleep an hour and a half or 2 hours.  I've tried putting him down sooner and I've tried later.  I try getting him to go back to sleep when he wakes up ..nothing works. He is swaddled the room is cool and dark. 
He was sleeping good at night and only waking once around 4 but now is up again every 2 hours.  He has also decreased how much he will eat at a time.  He went from taking 5 oz every 3 hours to sometimes 4 and sometimes only 3- 3 1/2.  He has silent reflux so the doctors say but every time I give him his Zantac he seems to struggle to eat and spit up (which he use to not ever spit up).  I guess I'm just at a loss on what to do and what is going on with him!