I know progress may feel slow at this point, but once you ring the second bell, the path is a little easier to follow for a while with Sen's fortress ---> Anor Londo. Easier to follow, but not necessarily easier to complete, hah!
Like Tolvo said, it might be a good idea to look at your weapon choice, if you can post your build at this point we might be able to see what weapon would be best for you.
Whatever you decide to go with, upgrade to at least +5 right away. You can buy the titanite Shards from Blacksmith Andrei in Undead Burg for 800 souls a piece. You will need 9 to upgrade it to +5 so 7200 souls + the 200 x 5 souls required for each upgrades. So for 8200 souls, you have a +5 upgraded weapon. Since you're there, why not upgraded to +10 (or close) with the Large Ember you should of collected form the Depth?
For that you will need to get a few Large titanite Shards. You can't buy them until later in the game, but lucky for you the Giant Leech drops them at a decent rate.
Don't farm for too long, you only need two to level your weapon to +7. You may already have 2 of them from drops or chests. Once you get the Covetus Gold Serpent ring, farming Large titanite Shards is a lot easier.
Of course, make sure you have a weapon you like and that is suited for your build. I know my last post was long and incomprehensive (like most of them), but it could help you find the best weapon for you.
The Demon in Undead Asylum is not a mandatory boss, but he does drop a titanite Slab 100% of the time. You can only get a few during one play through depending on how lucky you are with the Lizards. Slabs are very useful for end game weapon and armor upgrades.
Good Luck with Queelag, she is a very difficult boss the first time around. Very technical if you don't have a lot of fire resist armor!