Broken Windows startup after repartitioning drive
One should never try to change drive partitions under Windows (Boot Camp): this makes Windows unbootable. I do afraid that now you have to re-create boot camp partition and reinstall Windows. 

Anyway there're (proved by people) ways (see links 1, 2, 3) to achieve what you want. 

PS. I personally prefer and recommend external Thunderbolt drive for the 3rd partition shared between mac/windows