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.
The pain you describe is classic PE pain and what I also experienced. Stay calm and get some help with your littles. You need to rest--very important--and just take the meds they've given you. I'm betting once you deliver your baby, they'll run more tests to see if they can find a cause other than pregnancy. In the meantime, relax and take good care of yourself.
If you want, get your Urgent Care doctor to look into it more if you want.
I'm keeping you in my thoughts, friend.