I’ve doubted my [Christian] faith.
I want to point out that I and no doubt many others have had doubts. Some of the most devout Christians in history have been ones who discussed their doubts, or were even ardent atheists at one point. I believe in the Kirkegaardian idea that doubt is inherently required for faith; I think he specifically phrased it as "faith without doubt is credulity." I don't know if I'd put it that strongly, but I agree with the sentiment.
While I believe I've felt the Lord in my life more than once, I believe that not being able to directly see or communicate conversationally with Him is part of the point of faith, believing in what you don't know is true. Ultimately, I don't
know if the Lord - God - is real, or if His Son - Yeshua - was truly a divine sacrifice. I believe, but I don't know, and if I did know then it wouldn't be faith. It's ultimately a very simple, yet extremely hard test, in my view: to be right with the Lord, all you have to do is believe, and while that sounds simple, it isn't, and that's the whole point. And that's why I've never followed the atheistic argument of "There's no proof, so why believe?" The fact there is no proof is
why I believe in the first place. My faith isn't a matter of some desperate "No! I know God is there! I know it for a fact!" thing, but a "You're right, I don't know if God's there, but I choose to believe He is." At least in my opinion, that's what faith means.
If I knew God was there, believing in Him would be no different than believing cows (the dairy kind) exist. Knowing something is extremely easy, believing in something for which you have no evidence for or against is hard, and that's why faith is like a mustard seed. Sounds extremely simple, but it's hard to find and easy to lose. It's also what I feel answers the other common atheistic argument of "If God is real, why doesn't He just show Himself and fix everything?" Because, 1, He
did show Himself and our response as the human race was to murder Him, and 2, because what test of character would that be? This world is not His. It's corrupted and doomed by our own wickedness. The world isn't to be saved, it's those in the world who believe on Him that are to be saved. If He were to show Himself (a second time, and more definitively that is), what would that create except "belief" out of convenience for so many people? People who actively partake and promote wickedness and curse Him and those who believe in Him otherwise?
It doesn't require anything to know something, while it requires everything to believe in something, and it's very hard. This is all just my opinion, though.