I wouldn't say you have a northern accent, but people from Jersey do have a distinctive accent that says "I'm from Jersey". It's just different from a northern accent, just the way a Boston accent is different. I'm from Texas and when I go north people hear an accent, but it's not the typical southern accent - it's unique to Texas. Louisiana is another place that has a distinctive accent. There aren't too many places like that, but Jersey is definitely one of them.