Like what if I'm actually being controlled by evil to think I'm a Christian when I'm not?
I've had similar thoughts thinking to myself 'what if I've just been fooling myself this whole time and am really unknown'? Fortunately, that line of thinking is the actual foolishness. You can test yourself to see if you are saved or not.
If you believe Jesus exists and is the Word that became flesh and was raised by our Father and confess such with your lips, you know you are saved. We can't know about someone else's state of salvation, but we can have a pretty good idea by seeing how they live. If one professes with their lips but not their heart, their heart will betray themselves and it can be seen by their fruits. So really there are three types of people 1)Those who are saved 2)Those who are unbelievers (and not saved) 3) Those who are hypocrites and think they are saved when they are not. So, ask yourself, what do your lips say and what does your heart reveal?
Romans 10:9-13
If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. 10
For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved. 11 As Scripture says, “Anyone who believes in him will never be put to shame.”
12 For there is no difference between Jew and Gentile—the same Lord is Lord of all and richly blesses all who call on him, 13 for, “Everyone who calls on the name of the Lord will be saved.”[c]
The purpose of the gospel is to bring light into the world, to divide the darkness from the light so Elohim will know who are His, and who are not.
John 3:19
And this is the condemnation: that Light is come into the world, and men loved darkness rather than light, because their deeds were evil.
Everyone, absolutely everyone has darkness in them. When the light comes and exposes our darkness, Elohim wants to see what we will do. Will we reject the light to dwell in darkness? Or will we love the light for exposing our sinful nature? If we reject the light, we reject Elohim. If we embrace the light, we are saying to Elohim 'I do not want to dwell in darkness anymore. I choose your light, over myself and the darkness I dwell in.' Choosing the light is the first step, walking in it will be a lifelong process, and can be painful as we aren't even aware of all the darkness in us and how attached we have become to it.
So the question is, do you want to dwell in the light, or in darkness? What do your lips say about Jesus? What does your heart say?