Suggestion: Don't use the D&D vampire in a game as a PC in a normal party.
He's too powerful and too restricted at the same time.
Can't enter a house without being invited, can't be exposed to sunlight, can't be immersed in running water, can't be invited to ice cream socials, er waitaminnit.. Nevermind..
ECL is really hard to apply to a vampire, especially when you keep in mind that anything it slays is going to join him in 1d4 days as a slave. Heck, just being undead affords many advantages, not to mention all the 5 bonus feats and 56 skill points..
But how do you play in a game with those restrictions?
You might want to come up with a different kind of vampire to play as a PC.
If you really want to use the vampire template as written in a D&D game as a PC, go read this first and look at every single one of it's abilities on the chart here both to familiarize yourself with little details you missed, and to understand the relative impact of each before playing.
http://www.webspawner.com/users/soldarin/
Best guess I can offer is +10 though I don't know how playable a creature is 10 level levels behind even with all those special abilities. But really, look at all he's got. And look at all his penalties too... The D&D vampire is not well suited as written to be a PC. Maybe make a Buffy or Blade vampire instead.