I'm 27 years old and recently found a lump in left breast near my armpit, it's painful to touch.

I have itchy skin and sometimes it feels as if my nipple has created discharge, I went to the GP they noticed a considerable change in breast tissue when I was checked out I explained everything I was experiencing but they weren't concerned because of my age. 
 

I'm normally a fit and healthy person but I'm constantly feeling tired and have a nerve type pain in my shoulder and stiff achey neck. I've also noticed so many bruises when I have no reason to have bruises. 
 

im freaking out and I don't know what to do, do I seek another opinion from a different GP. I feel like every ache and pain is causing me such anxiety because I don't feel like I was listened to because of my age 

thanks for taking the time to read :)