Stefan, I would suggest to you that you differ from most people...not at all.
All of us "do better" when we are walking more closely with the Lord. My prescription for your "mental illness" is to immerse yourself in time spent with the Lord in His Word, which is one of the surest ways we have to allow God to communicate with us.
If you stay in His Word you are going to be less likely to entertain notions about other religions. All of us, having some knowledge of Scripture, can sit around and devise philosophies when we remain distant from the very Word that offers cleansing for our understandings and this is going to impact how we live our lives.
As far as questioning your salvation, my friend...that is a great indicator of salvation, in my own view. Religious people seldom doubt their salvation, and mentally ill people are not usually aware they are mentally ill. Some, like yourself, perhaps, think they are...because that is what they have been told they are. However, if you listen to what God has to say to you, and about you, I am quite confident that your "moods" will be improved.
Scripture demands diligence of disciples, and it isn't easy all the time, but, one thing I know from personal experience is the more time I spend with God in His Word, the more my own "moods" remain content. We can all, in the circumstances we are in, get depressed and unhappy at times. So don't overlook the resources you have as a Christian, the first being your relationship with the Lord Himself.
As I said, I am convinced of the power of the Word of God to change our hearts and lives, and to direct the quality of life we have. Doesn't mean circumstances are going to be easy, but, we will be better able to navigate when we are seeking to be close with the Lord. As one preacher mentioned, people are always asking what God's will for their life is, and the simple answer he gives is holding up his Bible. It's right there for us to learn.
And if you ever need someone to talk to, let me know. I was a drunk and a druggie and have some experience with court-mandated "intervention," lol.
God bless.