Welcome, WildeSilas. It's always nice to see new faces, and since you know some history as well as Greek and Hebrew, that means you can add depth to our conversations.
And since you brought it up, what convinced you that you we're "just making this all up in my mind?"
It was many things, too many to detail here. Some specific examples would be:
1) Prayer - despite the assurance of the scriptures that God does hear and answer prayer (though not always in the way we want), I can't honestly say I never saw a specific answer to prayer. Now keep in mind that I not only prayed continually on-and-off all day for almost 25 years, but have also prayed for specific things for people - healing, guidance, wisdom to navigate difficult situations, etc. In most every case, I found that I was eventually left to my own devices to figure out what to do, where to go, or how to handle something. Of course, I tried to use the scripture as a guide, but there are many specific situations in life and counseling where you can only apply biblical principles, but specifics must be decided through some other means. In my case, I wanted to rely on the Holy Spirit, but I can't say that I ever once had any kind of conviction or internal push to do one thing or the other. What I did find however, was that when I made pragmatic decisions based on logic and evidence, it was usually a right or "good" decision in the end. When I did not consider logic and evidence, but rather acted "in faith" for what I thought was the will of God (or should be, according to the biblical principles applied in the situation), the decision typically led to disaster, heartache, and confusion. This became very distressing to me over time as I found that acting in concert with faith (when it contradicted logic and reason) ended badly. It's too much to go into here, but suffice to say that as a result of 25 years of doing this, I ended up bankrupt, despised by the people I was ministering to, on the brink of divorce, physically ill, and fearful for my own physical safety (this all has to do with the fact that I pastored an extremely poor church in the middle of gang-land Little Rock, Arkansas, and physical threats were not uncommon, nor was hunger, poverty, dysfunction, etc.). Either way, after 25 years, I had no "miracle" stories to tell, no inspiring anecdotes of how "God came through" at the last minute to rescue me or anyone else. What I did see was however were the natural consequences of irrational decisions (based on faith) and irresponsible reliance on God to deal with situations where police, psychologists, physicians, and social workers would have been a million times more helpful.
2) Spiritual Growth - despite being a very intense student of the bible, pursuit of mission work, constant prayer, service, and even willingness to sacrifice my life in the work of ministry, I found that after 25 years, I was still pretty much exactly the same person with exactly the same quirks, sins, and struggles that I had been at age 15. I gained a lot of experience and knowledge for sure, but no increase in what Paul refers to as the Fruits of the Spirit. I witnessed this same lack of change in the people around me. If the Holy Spirit makes us "new creatures" and abiding in Christ makes us more like him, why was I simply becoming more like myself, and more like my parents, from whom I've inherited much of my nature? I honestly couldn't point to a single thing in my personality, character, or "spirit" (if you will) that was different as a result of following Jesus all those years. Either something is wrong with the promises of scripture (i.e. there IS no Holy Spirit), or something is wrong with me. Well, of course there's something wrong with me, I'm a sinner, right? I can't achieve Christ-likeness through works. I hope it doesn't sound like that's what I was trying to do. I list these "works" as evidence that my faith had muscle to it - these things were (I felt) a natural response to salvation and being a "new creature" - not the means to it. That said, I was earnestly seeking to be changed, to commune with God, to have a close relationship and communion with him. But in the end, I have no sense that anything supernatural ever happened to me. Any "experience" I had can be easily duplicated by listening to a stirring speech, seeing a movie that moves me, or listening to Octavarium.
I could go on, but the lack of change, lack of seeing tangible answer to prayer, along with constantly having to play theological whack-a-mole with contradictions and competing doctrines made me face the fact that while the whole thing would be awesome if it really were true, and if it really worked, it simply wasn't and didn't. Low and behold, I changed the way I made decisions, stopped praying and looking for answers in the scripture and BOOM pretty much everything in my life straightened out, started to make sense, etc. I also became a better husband and father because I had more time and attention for the things of earth. All the patience, devotion, peace, contentment, financial security, and peace of mind I'd sought through scripture and a relationship with God, I found outside of that whole mindset and culture.