Sqlite multithread update database WP8.1

I'm developing App wp8.1. And work with SQLite. I stuck with problem when multithread update database, I try something and see a bug like this, Database is locked or Busy. I use this code:

Task.Run(delegate()
            {
                GetList_Story();
                GetList_Category();
                GetList_Story();
            });

In 3 method like this:

async public void GetList_Source()
    {
        var postrequest = (HttpWebRequest)WebRequest.Create(ServerApilistsource);
        postrequest.Method = "GET";
        postrequest.CookieContainer = new CookieContainer();
        HttpWebResponse postresponse = (HttpWebResponse)await postrequest.GetResponseAsync();
        string response = String.Empty;
        if (postresponse != null)
        {
            var postResponseStream = postresponse.GetResponseStream();
            var postStreamReader = new StreamReader(postResponseStream);

            response = await postStreamReader.ReadToEndAsync();
        }
        listsource = Newtonsoft.Json.JsonConvert.DeserializeObject<ListSource>(response);        
        //if dont have table then create table

        foreach (var source in listsource.items)
        {
            DBHelper_Source.UpdateSource(source);
        }
    }   

Please Help me ?