Hoarding

My husband and I have been married 16 years.  He is a wonderful man but he brings things home and piles them in a corner saying that they will probably be needed one day.  His piles have spread out.  His car is so full of stuff that he can't even drive it.  We have to use another car.  I am continually cleaning out our back room to make it functional for company.  Our yard is beginning to get out of hand from things and wood that he has accumulated.  I don't know what to do.  He will not go with me to see someone about getting help.  I feel pretty confidant that he has ADD.  But would like for him to be tested.  What do I do about all the clutter?  I feel on the verge of a breakdown.  Should I get someone to help me clean it up.  Or wait for him to come around.  He usually makes excuses for dealing with it and goes and does something he would rather do.  How can I encourage him to quit hoarding. Our ability to communicate fluctuates from farely decent to off the chart.  Any advice  HELP!