I googled some key words and found several possibilities, but it definitely would take further investigation, i.e a good primary care practitioner to do a thorough history and physical, IMO. Here's a snip from one search of "breast numbness" :
 
<<The following medical conditions are some of the possible causes of Breast numbness. There are likely to be other possible causes, so ask your doctor about your symptoms. 

Incorrect fitting bra 
Diabetes 
Peripheral neuropathy 
Peripheral nerve trauma 
Peripheral nerve compression 
Cold 
Trauma to the breast 
Cerebrovascular accident 
Breast injury >>
It seems you could rule out trauma, cerebrovascular accident, and breast injury. The brownish discharge may not be related to the breast numbness as it could be normal leaking of colostral fluids.  I would also like to thank the listmothers for the fine job they do of moderating this list, keeping it on topic, and reminding us to stay respectful and professional. I much appreciate their recent posts. Laurie Wheeler, IBCLC, MN, RN Mississippi, s.e. USA 
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