Abraham as a great man of God gives me some comfort. He tells me that great men of God still doubt. The man held up by the great Apostle Paul in his letter to the church in Galatia (Gal 3 v 6) as a man of faith, needed reassurance.
God had given him a great promise that his descendants would number more than the dust on the earth. (13 v 16)
Abraham had heard God's promise but yet later he was back before God saying are you sure about this God. Surely this many descendant thing starts with one and time is ticking. (15 v 2)
God had promised him a country that would belong to him. (13 v 17)
Again he doubts and asks God for confirmation. (15 v 8)
The great thing is that God can handle doubt better than we can handle it ourselves. Doubt is an opportunity for God to give you assurance.
Abraham's doubt drove him back to God and far from beating him up for doubting he gently confirmed the promise.
Don't be scared of taking your doubts to God. We see doubt as failure, God sees it as an opportunity to show his faithfulness. Fundamentally, doubt is a process that should bring us closer to God, rather than the reverse.