Now whatever is wrong with being gay or bi, darling? You're practically a mature adult now, your parents don't need to follow you around whenever you go out on a date. And anyway, being 25, you're pretty much mature enough to make your own decisions regardless of what your parents think. I'm not too sure my parents know this about me (which I really don't care if they do) but I myself am bisexual and I understand what you're going through. Although it is true that there are a lot of people who are unreasonably prejudiced against people who are gay or bisexual, I think you should choose who you want to date. Gender matters not, it's the significant other's personality and actions that REALLYmatter.
Now, I'll be honest with you, I am bisexual, but I don't date girls (for the safety of my reputation and well being). You don't have to follow my footsteps on that if you don't want to (and I don't recommend it really).
But what really matters in the case of your situation, you are 25, your parents do not have to follow you everywhere like you're a child, and YOU are the only one to determine whether you want to date men or other women without anybody else's judgments. I hope what I said is very helpful. Remember, be true to yourself and others (even if some of those others disapprove). By the way, other than the fact that autism makes one have some social issues, whatever is so disappointing about having it? People with autism can be the smartest people in the world if they follow the path of what they're passionate about. Why, Albert Einstein had autism and he's very famous for being very intelligent (his brain was, in fact, discovered to be huge!)