If the bible says to repent and turn away from sin, why are others telling me I can't?

I'm curious because the bible says to stop sinning, fight the temptation to sin, not to live in sin. But the church and other christians say to me when I ask them that you can't and won't stop sinning. But doesn't that nullify repentance? My aunt told me that that calling myself a christian while living in perpetual sin the bible says is blasphemy of the holy spirit because I am chosing to remain in sin and call myself a christian? Say for instance, I am a fornicator and the bible speaks against fornication and that I shouldn't be doing it. But I insist that I am a saved christian living in sin with the right to attend church. My aunt says that the bible says that the children of the devil continue to stay in sin, it is a sin. I think that is in the book of John she said. My fellow congregation and pastor says that I am alright, but the bible as I am reading says I am not for chosing to I guess fornicate. What gives?