3 ways to tell.
1. Your reaction when things fall apart.
Do you catch yourself saying, "God, why is this happening? I've done x, y, and z?" Do suffering, difficulty, and obstacles provoke "why?" questions predicated on your goodness or effort? You've been working so hard, reading your Bible, going to church, serving others . . . why would God let this happen to you now? If that's your line of thinking, it reveals you believe God owes you. And that's religion.
2. Your reaction to others.
Do you compare yourself, bad or good, against others? Do you belittle, mock, condescend, even if just internally? Do you resent others' successes? Do you celebrate others' failures? Do you really wish people would get their act together, or do you really wish people knew Jesus? Are you frequently annoyed, put out, irritated, embarrassed, or inconvenienced by others?
3. Your appraisal of Jesus.
Is he your greatest treasure? That's the number one indicator of gospel-conformity. You may know right off the bat if this is true or not. For some, it's true only sentimentally or religiously. You may think it's true ultimately, but your time, talents, words, emotions, and bank account testify differently.
These are all heart issues. Anybody can get the behavior right. The Pharisees certainly did, and most of them went to hell. But this isn't even about looking Pharisaical or legalistic or churchy. There's a lot of Christian hipsters out there in coffee shop churches who have no idea they're just religious.