Breast pain.

g895756

I'm a 30F that's been having inner left breast pain for the past few months. It's not a horrible pain, just a dull ache with some itching. I've had an ultrasound of the area and a bilateral breast MRI both coming back negative. I've now started having upper and lower back pain over the last few days. I've been examined by my OB, GP, and Breast specialist. No one can find any cause for the breast issues. I’ve noticed my left breast hangs a slight bit lower than my right and my nipple is almost always erect. Should I get a second opinion on the MRI? Also my GP was looking back at vitamin D bloodwork done in Feb 2019 while I was pregnant and noticed my Vit D levels were an 8.4. Normal levels are 30-50. Could extremely low vit d levels cause back pain?