What Causes Sharp Pains Below Left Breast With Normal X-ray?

Question: I had a DVT in 2012 while pregnant with my son. In a scan at about 3 months postpartum, the clot was long gone with no vein damage. I was on Warfarin for about 3 months PP and Lovenox my entire pregnancy. I have always had quick sharp pains (lasting seconds) below my left breast for as long as I can remember (even as a younger adult...before being pregnant). They come and go very fast. Lately, I am getting them more frequently, mostly while laying down. This past week, a bit of soreness has lingered in and around the breast area and out to my left side. Sometimes the pain feels deep though like it could be under my left shoulder blade. I went to the ER last week because I had a series of PVCs (I have been diagnosed with benign PVCs) and this pain. They did a ddimer which was 137 ng/ml, a chest xray, and an EKG. All were normal as was my other blood work. My hemocrit was a little high (the high end of normal) which I have read can be tied to a pulmonary issue. The pain is not worse if pressed on (except under my shoulder blade). At any time I might feel pain in the front of the shoulder, under the breast, on my left side, or under my left shoulder blade. Should I look further into this issue? Could it still be a clot with a normal x-ray and negative ddimer? I am told that a neg ddimer is not 100% accurate. I am also supposed to have an Echo soon to rule out a heart valve issue.