I have to press hard on the brakes to stop car

Most likely there's a problem with the power brake booster. It could be simple, like a collapsed vacuum hose or bad check valve, or could be something like a torn diaphragm in the booster which would then require replacement. It could also be other problems in the brake system, like a failed master cylinder. Get it checked ASAP, brakes are a safety item. If you want to find a Nissan specialist, here's our directory link for you: https://repairpal.com/nissan-repair-in-fort-pierce-florida