Ah, yes. So you've found yourself a zombie. Zombies can make great partners, especially for Aspies-- they're relatively low-maintenance partners (except, of course, for reattaching lost digits), they also suffer from difficulty with eye contact and body language, and they're great listeners-- which is advantageous when one inevitably starts rambling about one's interests in the way we tend to do. You may find, however, that conversations with your zombie significant other are rather one-sided; zombies are usually not very verbose, and you certainly never have to fear him talking your ear off (although you'll certainly want to take great care to avoid him biting it off, because that is far more likely). This is because he is undead. You see, the undead are actually far less accustomed to articulating themselves than even Aspies. This is not to say they aren't social; on the contrary, they can be quite sociable. Zombies are actually in their element in the midst of large groups or crowds, and they have even been known to congregate in parties the size of entire cities. The problem is, rather simply, that their verbal skills are underdeveloped. If your relationship is going to work, then you're going to have to learn ways to work around this. So here's my advice:
- First of all, from what you've said here, I really don't think he's "using" you just to get to your brain. Zombies tend to fixate on brains, that's true-- but oftentimes that's nothing more than a superficial reflex. If you read between the lines a little (which I realize is not an easy task for many Aspies), you're very likely to find that he really is interested in all of you-- your stomach, your intestines, your spleen, and most importantly, your heart.
- I would also remind you that all relationships go through communication troubles. It's perfectly natural. Communication is the cornerstone of any lasting relationship, but it's not something you can rush. Remember, Rome wasn't built in a day (or a night, or a dawn, or even 28 days later). Be patient.
- If you're having difficulty getting him to participate in conversations, it could be that he's uncomfortable around you, or that there's just not much to talk about. In either case, try doing more things together. Rent some George Romero movies to watch with him. Or take him out to eat at a nice restaurant (just make sure you go when there are plenty of customers for him to dine on). Things like that are great conversation catalysts. When he feels at ease with you, then you may find him much more willing to chew the fat.
- Finally, if all else fails, there is one last option. But be warned: this is a last resort, only to be used if there's truly no other option available. First, you'll want to ensure that there are no shotguns, handguns, blunt instruments, or vinyl LPs of Dire Straits or Sade lying around. Once you've done that, sit him down and have a heart-to-decaying-chest-cavity with him, tell him how important he is to you-- and then, let him bite you. A little nibble is all it takes. Soon enough, you'll realize you have so much more in common with him than you first thought-- and even better, you'll totally be on the same wavelength conversationally.
I hope my advice proves helpful. With a little work, your undead relationship will last a long, long time-- at least, until one of you takes a fatal blow to the head.
Good luck! May you two enjoy the zombie apocalypse together! 
_________________
Mediocrity is a petty vice; aspiring to it is a grievous sin.