thats why you have to use head movement to avoid their jab and get inside or in your range. you can't jab them if you are at their range, you can't jab if you are too close... when you get deep inside you can't jab because you don't have the range, do you know how to hook?

Jab your way in. Basically you just need to improve your counter punching, range, footwork and head movement... (just get better at boxing... there is no quick fix you'll need to develop the skills to work the right tactics)