UNITY 2D: Player flying when space/mousebutton is holded

Question

So basicy i need my character to go up when space or mousebutton are pressed. I added rigbody 2d and box colider 2d to my gameobject (player). The problem is when I hit space or mousebuttonit only jump not constantly moving up.

Here is my code:

using UnityEngine;
using System.Collections;

public class PixelMovement : MonoBehaviour {

    Vector3 velocity = Vector3.zero;
    public Vector3 PressVelocity;
    public float maxSpeed = 5f;
    public float fowardSpeed = 1f;
    public float jumpForce;

    bool didPress = false;

    // Use this for initialization
    void Start () {

    }

    //Do Graphic & Input updates
    void Update()
    {
        if (Input.GetKey(KeyCode.Space) || Input.GetMouseButton(0))
        {
            didPress = true;
        }
    }

    //Do physics engine updates here
    void FixedUpdate()
    {
        velocity.x = fowardSpeed;
        if (didPress == true)
        {
            didPress = false;
            velocity += PressVelocity * Time.deltaTime *jumpForce;

        }

        velocity = Vector3.ClampMagnitude(velocity, maxSpeed);
        transform.position += velocity * Time.deltaTime;
    }
}

Answer 1

Ok this works for me. Thanks everyone for help :)

using UnityEngine;
using System.Collections;

public class PixelMovement : MonoBehaviour {

    public float playerSpeed;
    public Vector3 gravity;
    public float maxSpeed = 5f;
    Vector3 velocity = Vector3.zero;
    public float fowardSpeed = 1f;

    bool didPress = false;

    void Update()
    {
        if (Input.GetKey(KeyCode.Space) || Input.GetMouseButton(0))
        {
            didPress = true;
        }
        else
        {
            didPress = false;
        }
    }

    void FixedUpdate()
    {
        velocity.x = fowardSpeed;
        transform.position += velocity * Time.deltaTime;
        if (didPress == true)
        {

            float amntToMove1 = playerSpeed * Time.deltaTime;
            transform.Translate(Vector3.up * amntToMove1);
        }
        velocity = Vector3.ClampMagnitude(velocity, maxSpeed);
        transform.position += velocity * Time.deltaTime;
    }
}