Wordpress returns the same Post ID every time everywhere!

There is something weird happening in a recent theme I have developed.
Inside the post page when I use $post-ID and get_the_ID() it always returns the same ID which belongs to one of my posts!
I'm wondering what's happening there?!!!

Edit: I found the reason behind this behavior. And it is that I have created a widget which inside it I use the WP_Query class (you can see the code at the end) and I guess it's overwriting the global $post.

class TextAds extends WP_Widget{

function TextAds(){

    $widget_ops = array( 'description' = __( "نمایش تبلیغات متنی", 'appthemes') );

    $this-WP_Widget('textads', __('تبلیغات متنی', 'appthemes'), $widget_ops);

}

function widget($args, $instance){

    //global $userdata;

    extract($args);

    if ( !empty($instance['title']) ) {

        $title = $instance['title'];

    } else {

        $title = 'تبلیغات متنی';

    }

    echo $before_widget;

    $title = apply_filters('widget_title', $title, $instance, $this-id_base);

    $term = get_term_by( 'slug','text', 'ad_cat' );

    $text_query = new WP_Query( array('post_type' = APP_POST_TYPE, APP_TAX_CAT = $term-slug, 'ignore_sticky_posts' = 1 ));

    ?

                    h2 class="widgettitle"?php echo $title; ?/h2

                    div class="clr"/div

                    ?php while ( $text_query-have_posts() ) : $text_query-the_post(); ?

                        div class="ad0text"a href="?php

                        //$url = get_post_meta(get_the_ID(),'cp_url',true);

                        if(stripos($url,'http://') === false){

                            $url = 'http://'.$url;

                        }

                         echo $url; ?"?php the_title(); ?/a/div

                        div class="divider"/div

                    ?php endwhile; ?



    ?php

    echo $after_widget;

}

function form( $instance ) {

?

        plabel for="?php echo $this-get_field_id('title'); ?"?php _e('عنوان ابزارک:', 'appthemes') ?/label

        input type="text" class="widefat" id="?php echo $this-get_field_id('title'); ?" name="?php echo $this-get_field_name('title'); ?" value="?php if (isset ( $instance['title'])) {echo esc_attr( $instance['title'] );} ?" //p

    ?php

}

    function update( $new_instance, $old_instance ) {

        $instance['title'] = strip_tags(stripslashes($new_instance['title']));

        return $instance;

    }

}