When should I go to ER?

I have been experiencing problems with shortness of breath with my dilated cardiomyopathy/heart failure.  Last EF was 20-25%.   I have shortness of breath with walking.  Sometime I wake up with shortness of breath in the middle of the night.  Sometimes I wake up and have it for an hour or so.  Other times I have it with sitting in recliner for 5 hours.  I am 49. I have always had a physical job and I am struggling.  I went to the ER when the shortness of breath would not go away.  They put me on oxygen for a few hours and sent me home.  Also did EKG's and blood work.  I really wasn't told anything.  Two days later I had trouble again but I didn't want to spend money going back.  What am I supposed to do?  Am I causing damage by not getting the oxygen?

[CCF HeartMD3]

bkem,
Congestive heart failure is a chronic condition that can make you retain fluid and feel short of breath. While it is a chronic condition, with frequent contact with physicians, compliance with medications, checking daily weights and following a strict no salt diet. I would recommend seeking care with a cardiologist who specializes in the treatment of patients with heart failure. Many large hospital centers will have home health programs that monitor daily weights and help ensure that you are not keeping an excess amount of fluid.