I don’t think there’s any Christian that exists whose faith has never wavered. Sometimes we just have a hard time believing what God said is going to come to pass when we look at our circumstances. The great thing about the Bible is there is story after story of people that God promised things to (that humanly speaking couldn’t come to pass), but with God all things are possible.
God promised Abraham a son even though he and Sarah were way too old to have one. (Romans 4:19-KJV says that Sarah’s womb was dead) and we know that they had a child meaning God brought it back to life again. God is faithful to all the promises He makes to us, we just need to believe His Word. Find a witness in the Bible who already went through what you’re going through and read how God made a way for them. Whenever my faith is wavering I read Hebrews 11. It is literally a whole chapter of people in the Bible who had faith in God. Just from these stories, we can learn to trust God which is why faith comes by hearing the Word of God. (Hebrews 11:2- Men of God in days of old were famous for their faith.)
It’s important for us to encourage ourselves in the Lord. I love reading the book of Psalm because no matter what David went through he continued to praise God. He meditated on God’s Word and reminded himself of the things God did for him. He had faith that the same God who did it before will do it again. There’s a song by Marvin Sapp called “Praise Him In Advance” about praising God in the good times and when things are going bad. That song has helped me tremendously because praising God no matter what’s going on reframes my circumstances. It helps me walk by faith, not by sight. Also, as Christians, we should study Jesus' life to see how He overcame. He spent much time in prayer and He always prayed the answer: what God said was the answer, which is God’s will. He never spoke the problem, only the desired result.
God promises us things, but we must believe what He says to show Him that we have faith. There’s nothing wrong with building our faith back up. It may be wavering right now, but it doesn’t have to stay that way. We need to read the Bible to build our faith back up and believe His promises to us.