It's cross to bear, bear in this case being used in the same sense it is in weight bearing, Greeks bearing gifts or even ball bearing. It refers back to the Biblical tale of Jesus carrying his cross to Golgotha.
Lookin' Out My Back Door. Lookin' Out My Back Door is a song recorded by the American band Creedence Clearwater Revival, also known as CCR. The song was written by the band's lead singer, guitarist, and songwriter, John Fogerty.
One of his notable songs from this tenure was from the film Destry Rides Again (1939), for which he wrote the lyrics to  See What the Boys in the Back Room Will Have , with music by Hollaender and sung by Marlene Dietrich.