Lamar Jackson isn't going anywhere -- the superstar quarterback just agreed to a humongous 5-year, $260 million deal to remain with the Baltimore Ravens ... making him the highest-paid player in NFL history. Jackson shared his immediate reaction via the Ravens' Twitter account ... saying, "You know, for the last few months, there's been a lot of he say, she say. A lot of nail biting, a lot of head scratching going on."