How is it possible to be morally "good" when you have to drink human blood to survive? And to get that blood you have to willfully injure the vessel? It's a trick question, you see. There's no way you'll remain morally upright if you remain a vampire.
If you're going to play a morally good character, you'd best focus on getting your vampirism cured. Or, deal with the fact that you got embraced into a murderous coven of bloodsvckers... and if you can't beat 'em...