Sorry for the long post just looking for abit of re assurance! 

So a couple of months ago my right boob felt really achy which also was felt under my armpit, I got this checked out at the Drs they said everything looked and felt normal no lumps etc so put it down to the strain of carrying my now 5 month old and probably hormones. Since then I have got shoulder blade ache which comes and goes throughout the day, everyday for the past few weeks. I also get a cold sensation sometimes down the back of my arm and also experience elbow and wrist ache every now and again, a dull ache. 

Been to the Drs and they again said it's probably from carrying my Son, although he plays and sits in his chair so I'm not carrying him all the time... I even went to the hospital as I was getting so paranoid about it being breast cancer that's spread to bone ( sounds dramatic but I'm just so paranoid I've never experienced anything like this ) 
They said it's more than likely a pinched nerve and just asked me if I had any 'common' symptoms of cancer e.g nausea, rapid weight loss, bowel issues etc and then said as I haven't got any it's not that. 
 

My breast feels dull and heavy but also achy and recently I have had a few sharp shoots pains in it and yesterday I pulled my top up and discovered the nipple looked slightly inverted/retracted so now I'm absolutely losing my mind self diagnosing myself, I keep pulling my top up and sometimes it is doing it and sometimes it isn't but it comes straight out again when I do lift my top up or touch it. I have a 5 month old and I'm just so scared about leaving him without me. I didn't breastfeed as he was a week early and my milk hadn't come in properly he probably latched on 3/4 times and then I gave up. Can this all just be something simple  

Any guidance or replies much appreciated!