Looks like you got great trouble shooting advice from fellow mommas. Sleep is such an important aspect to the health of a family...everyone is on edge after days of interrupted sleep...even baby. Sounds like a sleep issue and not a health issue,especially if you got baby checked out and he naps fine during the day. Sounds like it is solely a nighttime sleep issue.
I have never hired or know of anyone that has hired a sleep consultant. I do have a book and it is my sleep bible. All 3 of my kids are fabulous sleepers and have been since 2months old. It has sooo many helpful hints on what might have gone awry with your child. Give it a try. I have many friends who have borrowed my book when such issues as yours arise and sure enough they have tried out a method and it has worked.
The book is amazing...I can't say enough good things about it. It covers a wide array of sleep issues from newborns up to age..i think 5ish.
"Sleeping Through The Night. How Infants, Toddlers, And their Parents Can Get A Good Night's Sleep" by Jodi A Mindell,Ph.D
Good luck and I hope you have blissful sleep again in your near future.