I was stuck on level 26 for ages but the best thing to do is do the Vault of glass each week and also make a new character as same as you're using now, get that level 20 (it takes less than 24 hours if you power level all the way e.g bounties, increase the level on missions what you've done and PvP) if you do make a new character this means you can do vault of glass twice a week so make sure its the same character as you're using now because you can just put your stuff in the vault and then you'll have a greater chance of earning raid gear/weapons
hope this helped