There is a saying, "we can not give what we do not have."
It is hard to love someone if we have not experienced how much God, our Abba, Father love us. He showed His love by giving His only son Jesus Christ. (John 3:16). You are fearfully wonderfully made by God. Psalm 139, 138.
Maybe you should go back to your first love. Read His word. Declare and hold on to His promises. Fellowship. Pray for her. Ask, seek and knock at His door to give you practical ways to first love God with all your heart, soul, strength and body and to love your closest neighbor, your wife. (Mattew 7:7-12, Matthew 22:37-39)