Sprites looks blurried on fullscreen

Graphics
3

according to me I am not using any shader. Don’t know how i can disable bitmapping. Here is my drawing code:

        spriteBatch.GraphicsDevice.SetRenderTarget(renderTarget);

        //This will clear what's on the screen each frame, if we don't clear the screen will look like a mess:
        GraphicsDevice.Clear(Color.CornflowerBlue);

        spriteBatch.Begin(SpriteSortMode.Deferred,
            BlendState.AlphaBlend,
            SamplerState.PointClamp,
            DepthStencilState.None,
            RasterizerState.CullNone,
            null);

        spriteBatch.Draw(sprite, pos, Color.White);

        spriteBatch.End();

        spriteBatch.GraphicsDevice.SetRenderTarget(null);

        spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend, SamplerState.PointClamp, null, null, null);

        Resolution.BeginDraw();

        spriteBatch.Draw(renderTarget, new Rectangle(0, 0, screenWidth, screenHeight), Color.White);

        //Draw stuff onto the render target
        spriteBatch.End();

        //Draw the things FNA handles for us underneath the hood:
        base.Draw(gameTime);
    }