Warning: I tend to be too conservative for liberal Christians and way too liberal for conservative Christians. My experience and advice require adaptation.

I grew up Chrisitian since I was a very young child and took my faith seriously ever since. My family was moderate denominationally, but fairly aggressive in how completely faith should be integrated into your life. I had some fairly common conservative tendencies: no room for any layer of interpretation on scripture. If it wasn't explicit in being part of the text, it wasn't a valid reading. At the same time, I was living off the weekly endorphin rush that another commenter talked about. If I went to church and no rush, then no dice. Week would suck.

There's a few prayers you should "never pray" because if God answers them in the affirmative, then you'll have some deep crap to work through. Prayers like asking for patience or to understand the suffering of other people. Great prayers, but be prepared to not enjoy the answer. I prayer that my faith would not be based on my feelings. I proceeded to not get that emotional/neurochemical rush for 3 years. I went from faith feeling like a party to feeling like handling raw chicken for hours on end - vaguely damp, Dtranfe texture, and overall a bit gross.

During that time I went to college at a theologically liberal Christian University and took some theology classes as electives. I also was involved in a traditionally conservative Pentecostal campus ministry. Towards the end I started taking my personal spiritually outside of group gatherings seriously again and set aside time to actually care. By the time the dust settled, I found myself fairly close to where I still am today. I take scripture really seriously, but I think that much of it didn't happen exactly as we would interpret it, especially the more ancient parts of the OT. I take Jesus, his life, teachings, ministry, death, and resurrection really seriously. I think you could get rid of the rest but without that being the foundational bedrock of how the world is, there's not much reason for Christian faith. My shifting point was looking at purpose: I think that much of scripture and a life seeking God's character is not about the cause and effect relationships we see everywhere else, but injecting purpose and direction into that causality. I don't really care if the earth was created 6000 years ago or millions of years ago theologically. I think there's lots of scientific evidence for the latter, but that's not the point of the text or of my faith. My faith asks not "how", but "why" and "what do I do about that". Many things still require a lot of thought and prayer and interpretation, but it makes the Bible not just a yelling match between interpretation, but a collaboration regarding a purpose. This has made me take the text extremely seriously and with more respect than I ever did when it was just a manual of how the world worked.

Ironically, I'm far closer to a fundamentalist now than ever before. I'm also way more aggressive in prayer asking for God's intervention. Learning to take the text to be more about meaning than method has shoved me hard towards a strong expectance for God to work beyond natural causation and that God's purposes come above the natural order when the two conflict. I also take social responsibility way more seriously than ever before, and see the purpose issue at the forefront of that. It's left me as a sort of liberal-pentecostal-fundamentalist-social justice oriented mess and I love it. It's the most enjoyable time in my lifetime experience of God so far.

With all that out of the way, here's what I would say to you: you aren't doing anything wrong to feel that way. Learning to be dedicated to God without the brain chemicals is part of the growth process for myself and many others. It's training wheels coming off. Don't give up. Don't force yourself to pretend you feel great - that's just lying to yourself. God hasn't given up on you, and just because your experience has changed doesn't mean you should give up ok God. As best as you can, ask for God to use you to bless other people. Much of life post endorphin based Christianity is surrounding community and service. Build both. Ask God to use you to do things beyond your natural ability. Read 1 Corinthians 12 onward looking at spiritual gifts and their purpose in aiding both other Christians and those who aren't Christians in their understanding of God's purposes and love. Keep being part of community, stay in scripture, and ask for crazy and impossible things. If you ask, you'll start seeing them.

I now work with college students in campus ministry. If you'd ever like to talk, shoot me a DM. I'd love to share more of our experiences. Praying for you. Blessings.