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.

This doesn't happen to everyone, of course, and it didn't happen to me. However, there's a couple of big reasons why it can happen for sure. First, any kind of trauma like a PE can set everything off kilter for a while. Sleep habits, exercise habits, and eating habits can all take a big hit after a traumatic event like getting a PE.
Also, it might depend what medicine you're on. If you're taking warfarin/coumadin and feel hamstringed by dietary issues, that could be affecting things as well.
If it is neither of those, I would check in with your doc to talk about it. Anything that is of constant concern should be talked about, for sure. Maybe he/she will have something that will help put your mind at ease.
I would discuss with your doctor, if the matter concerns you.
All the best!