". . . Terrified of Living Your Own Life?"

I'd like to know what people mean when they say, "You're just trying to convince yourself . . ."

This is something that my mother and roommate have said to me when I tell them that I don't believe I will change my sexuality. Do they actually think that I don't believe what I say, or do they just not believe what I say and assume that deep down inside I also know that they are right? Do I act like I am just trying to convince myself? What does that even look like? What does sincere belief look like?

Just hoping you all have some insights I'm missing.