I have sever itching inside abdomen on both sides close to breast i try to itch it on outside to get relief it's that bad what could this be?

Few things: Hard to know without more information. Most likely may be heat rash, fungal skin infection, mite infection such as scabies, contact sensitivity to bra component (rubber or metal insert for example). Itching is generally generated by nerves in the skin and not deeper; even though the sensation is that it comes from inside the abdomen.