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.

Sorry to hear what you are going through. It's tough when you are having definite symptoms from multiple diseases but they can't figure out why. I've been on steroids for a few years now and I can report that I enjoy being able to breathe. :) For a very long time I had symptoms similar to yours, particularly when circumstances or the environment were putting greater demands on my heart and lungs. It's very possible that the symptoms you describe are just your body getting a tougher cardiovascular workout and pushing against the scars from your clots. Try to pinpoint any triggers that make your symptoms worse that you can control, for example:
- reduce irritants to your lungs - avoid cleaning fluids and perfumes, stay indoors on smoky or high pollen days, if possible run an air filter in the room you are in
- try to avoid retaining fluid - avoid salt
- try to stay in places with a moderate temperature - avoid high and very low temperatures and avoid humidity (air conditioning can be used to reduce the humidity in the house uf you have one, I live in a temperate rain forest and sometimes I run the air con for half an hour in the winter just to lower the humidity in the house)
- wear a looser bra, or get one of those extensions for your bra. Or lengthen the shoulder straps to pull the ribcage band lower on your chest where your ribcage is a bit narrower
- keep meals small - digestion uses a lot of oxygen, and a full stomach also reduces the space available for your lungs to expand
- have a short liedown several times a day when possible
- use pursed lip breathing (very easy, google for a short video) to increase your lung efficiency when you are feeling short of breath or exerting yourself
- plan outings for when you are feeling better - I do my chores in the morning and before I eat so it's easier on my lungs - and be careful not to overdo it because recovering from that takes me days
Also, try to keep notes on what you are able to do so you will know that you are improving. For me the improvements were so slow and gradual that I didn't realize I was better until friends and family pointed it out.
And finally, remind yourself that palpitations, tightness and chest pains are very common while healing, you have been checked out for anything that is immediately threatening, and you will get better.
I hope this helps.