I'm sorry you feel this way caitianx. I think I can say that I have felt similar in some ways, I know what it is like to be depressed about my baby side anyway. I think the biggest depressing thing for me was fear of relationships as an Adult baby, but I slowly got over it by deciding that being in a relationship didn't determine my ability to be happy, although it has taken a long time to convince myself of that, and I sometimes still relapse. I don't think there is any real reason for being ashamed of the adult baby side of one's self, sure there are side effects, but there are also positive things too, like how relaxed and calm you get to be when you baby out.
I really don't know if there is a great way to fight off depression, but I have always heard that exercise helps, also eating healthy.
Know what though, here is the number one thing. Just because you are autistic and have a tough time with the social world, does not mean you are a failure. Out of all the creatures in the animal kingdom, humanity is the one that is so smart, that we are too dumb to see how we have complicated our lives with social requirements and obligations. What does a lion do all day? Eat, sleep, chase things, mate, it is a pretty simple life. Humans on the other hand have to pay taxes and argue about if it is right for two unknown people of the same gender to be allowed to have a document that puts them on the same social standing as everyone else. Frankly, humanity screwed up life when they started to introduce all of the complexity. Sure there are a lot of advantages and necessary things about social interaction, but man! There is a lot of unnecessary crap that got thrown in too, and a lot of expectations towards people that don't need to be there. So if you are failing at meeting a social expectation because it is beyond your control, give it the bird, a lion doesn't know how to socialize in the culture we have, but it is pretty damn awesome anyway(weird analogy, i know). Just figure out what makes you unique and cool, and be proud of that. Think of a few of your favorite simple pleasures, and enjoy that you get to have those.
Good luck. Depression sucks.