There's 2 quests named Cleanse the Commonwealth and Quartermastry, they're repeatable and give about 200-300 XP a pop and just involve killing enemies at certain locations, they're for the brotherhood of steel, once you've joined, just google the police station they're located in and do the starting quest to unlock them. Just repeat those 2 quests and you'll get plenty of XP and goodies. Remember to have Idiot Savant unlocked whenever you can, because that perk is a god send, even at 11 INT