Adding momentum to jump while sprinting

I can't figure out how to add momentum when my player jumps while moving. it seems to work fine when i'm not sprinting but if i jump while sprinting it sort of stops mid air and moves the same amount as if i wasn't sprinting.

I was thinking the problem is when i'm jumping the player isn't grounded anymore so the movement speed is being set back to walking speed but i can't figure out hoe to do it.

public class Test : MonoBehaviour { public Camera playerCam;

 [SerializeField] private float speed;
 [SerializeField] private float walkSpeed;
 [SerializeField] private float sprintSpeed;
 [SerializeField] private float jumpForce;
 [SerializeField] private float jumpRaycastDistance;
 
 private float hAxis;
 private float vAxis;
 private float baseFOV;

 private bool isSprinting;
 
 private Transform player;

 private Rigidbody rb;

 private void Start()
 {
     baseFOV = playerCam.fieldOfView;
     player = this.transform;
     rb = GetComponent<Rigidbody>();
 }

 private void Update()
 {
     Jump();
     MovementSpeed();
 }

 private void FixedUpdate()
 {
     Movement();
 }
 
 //player movement
 private void Movement()
 {
     hAxis = Input.GetAxisRaw("Horizontal");
     vAxis = Input.GetAxisRaw("Vertical");

     Vector3 movement = new Vector3(hAxis, 0, vAxis) * speed * Time.fixedDeltaTime;

     Vector3 newPostion = rb.position + rb.transform.TransformDirection(movement);

     rb.MovePosition(newPostion);
 }

 //Movement speeds and camera FOV Change
 private void MovementSpeed()
 {
     if (Input.GetKey(KeyCode.LeftShift) && IsGrounded())
     {
         isSprinting = true;
         speed = sprintSpeed;
         if (isSprinting && vAxis > 0)
         {
             playerCam.fieldOfView = Mathf.Lerp(playerCam.fieldOfView, baseFOV * 1.25f, Time.deltaTime * 6f);
         }
     }
     else
     {
         isSprinting = false;
         playerCam.fieldOfView = Mathf.Lerp(playerCam.fieldOfView, baseFOV, Time.deltaTime * 6f);
         speed = walkSpeed;
     }
 }

 //jumping
 private void Jump()
 {
     if(Input.GetButtonDown("Jump"))
     {
         if (IsGrounded())
         {
             rb.AddForce(0, jumpForce, 0, ForceMode.VelocityChange);
             //rb.velocity += jumpForce * Vector3.up;
         }
     }
 }
 
 //Raycast to check if the player is gronded
 private bool IsGrounded()
 {
     Debug.DrawRay(transform.position, Vector3.down * jumpRaycastDistance, Color.red);
     return Physics.Raycast(transform.position, Vector3.down, jumpRaycastDistance);
 }

}