Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.
I found it hard because the symptoms during recovery were quite similar to the symptoms during the hospital phase. They will get better over time, though not as quickly as I'd like (hence my user name...). You probably feel like you've been hit by a truck - you've had the lung equivalent of a heart attack and it takes a while to heal.