Camera rotation with mouse but dont stop

I have a question I made a game where you controll an spacecraft and use the mouse/keyboard to move. I use the mouse to rotate the ship up, down left and right. Works like a charm. Only problem is when I stop moving the mouse the ship also stops. So If I want to rotate the ship a few times I need to run a marathon with my mouse. This is because I use the Input.Axis(Mouse X) and thats zero when you stop moving the mouse.

So what I want is: Rotate the ship lets say left if I move my mouse a bit to the left and only stop when I return the mouse to the centerarea. I have this code ATM

    var c = Camera.main.transform;
    float mouseX = Input.GetAxis("Mouse X");
    c.Rotate(0, mouseX * sensitivity, 0);
    c.Rotate(-Input.GetAxis("Mouse Y") * sensitivity, 0, 0);
    c.Rotate(0, 0, -Input.GetAxis("QandE") * 90 * Time.deltaTime);

How can I accomplish this

BugFinder's answer is correct. Here it is in code, for rotating around the Y axis. You can build on it to get your other axes working.

using UnityEngine;

public class Roll : MonoBehaviour
{
    public float sensitivity = .001f;

    Transform c;

    void Start()
    {
        c = Camera.main.transform;
    }

    void Update()
    {
        Vector3 mouse = Input.mousePosition;

        float dx = 0;

        if (mouse.x > 1000)
            dx = mouse.x - 1000;

        if (mouse.x < 920)
            dx = mouse.x - 920;

        c.Rotate(0, dx * sensitivity, 0);
    }
}