Nothing coming out??

My boobs fill so heavy, hard & full but when I pump I’m not getting anything (Usually I do) and when I express manually I get very little.

I don’t breast feed but my boobs have had some milk since the very beginning. I pump to bring in my milk supply because it never fully came in and I’d like to try breast feeding my baby as he’s having trouble with formula. Any tips on how to help bring in my milk supply?