Does difficulty breathing when lying down always mean heart failure? i'm 20 years old, how likely is it for me to have heart failure? i am overweight.

Get tested: To put yourself at ease, get tested by your physician or a referred cardiologist. It may be apnea related to your being overweight but check it out to be safe. Good Luck

OSA: I suggest with your symptoms and weight issue that you see a physician and have a sleep study to rule out obstructive sleep apnea. If you do not have a history of heart disease, or diagnosis with an echocardiogram, EKG and x-ray, I suggest that CHF would be much less likely.