I took a minute to look at the definition of the word "trust" before answering. The word that keeps repeating in almost every entry is "confidence". That makes sense, and it inspired some thoughts.
Confidence is necessary to human beings. We base
everything we do on confidence, in some form. We make choices between options because we're more confident in one than another. We give our confidence to others, and that's always a risk, because people are changeable.
Entering a new friendship is like putting your foot on unstable ground, guessing that it will support you but having no way to be absolutely certain. But if you never take a step -- never extend your confidence to anyone -- you go nowhere, and humans like to move. So in that sense, yes, we're all pretty trusting.
Too trusting is a matter of experience, though: If you have taken steps toward people (giving them your confidence) and have ended up hurt, then you will feel that you may have trusted too much. If your find that your confidence is well-founded, then you will believe you trusted just right.
So no, I don't think you're
necessarily expecting too much, not given the small amount of information you've shared here. What you may be doing is failing to see patterns in yourself and the people you choose to trust, to learn which patches of ground may not be able to support you, for whatever reason. That's not uncommon in autistics. We can really suck at that kind of assessment, but we can learn methods to improve.
You didn't ask for advice, but I would suggest you make some notes about each of your friendships, including:
Trajectory - How fast did the friendships develop? Where did you notice things starting to go wrong?
Personalities - What traits attracted you to these people?
Investment - What and how much did they put into the friendship?
Personal - What and how much did
you put in? Exactly which expectations weren't met?
Then look for patterns in what you've documented, both in your friends' behavior and your own. What you find may be very informative for future choices. You may see a common trajectory you can analyze for your own part in it as well as theirs. You may see that the traits which tend to attract you may be uniformly consistent, and based on your history, may not be the right ones to look for. You may see a pattern of distinct imbalances of investment. And so on.
This may not be the right exercise for you, but it at least may give you an idea of another way to really study your history.
It takes two people for a friendship to succeed or fail, so becoming a more educated consumer of relationships can help you ensure that you're really doing the right things, and putting your confidence in the right people. Sometimes we Aspies and Auties may just need to get a little academic to work this stuff out.