"Has God indeed said, 'You shall not eat of every tree in the garden?'" -Genesis 3:1B
Doubt is a dangerous weapon of the enemy. Satan understood the bower of doubt and used it against Eve. You could even say that, because of doubt, sin entered the world.
"He who doubts is like a wave of the sea, driven and tossed by the wind." James 1:6B
James understood the power of doubt and its danger to a believer. Very few people are exempt from doubt, but those who experience it still need to know a way to combat it.
1. Confess the doubt to God as Sin "He who doubts is condemned... ... for whatever is not from faith is sin." -Romans 14:23
2. Study the Gospels, especially the later part where Christ has conquered death. It is good to read these constantly to remind us what we believe.
My admonition, Pray to God and Study his Word. These are things we can always do more of.
Your Brother in Christ,