It's all very well having a pop at other people for being inconsiderate, but there are probably plenty of people who get irritated by what you do too.
The guy who cut into the queue - perhaps he didn't notice you? Did you say "excuse me, I was here first" or did you just accept it? I once cut in accidentally because the real queue was hiding up a supermarket aisle, and the person at the front was leaving a huge gap (well over 5 metres). Nobody said anything either, I only realised when I turned round to find everyone glaring at me! It's unusual for people to genuinely, blatantly cut in when they know they're in the wrong. Did you both arrive in the queue at more or less the same moment? Or was it the sort of place where there are separate queues for self-service and for attended checkouts, and he didn't realise there was another queue? You've not given enough information.
The man who blocked you in "when he didn't need to" - perhaps there was an emergency? What did you do to make him aware of the fact he was blocking you in? How do you know that he knew that you couldn't get out? As for people driving like lunatics, if they are jumping traffic lights or breaking the law, make a note of their number and report them to the police.
Unfortunately, when you send your child to school, them catching an illness off another pupil is par for the course. I can assure you that your own child will pass an infection onto someone else at some point during their time at school, and no doubt their parents will be bemoaning what a selfish parent you are for sending your child in sick.
You say that "you're not openly crap to people" - well, good! But what about all the people you are accidentally crap to?
As a rule, when people complain that others are being selfish, it is usually the complainer themselves that is being selfish. "Mr X didn't do what I wanted, he's being selfish." "Ms Y couldn't come out for a drink after work, she was too busy to come out with us." You are disappointed that people didn't do what you wanted, you are just as selfish as they are.
You say you've abandoned this thread because people are judging you. You asked whether you're being unreasonable, and you got a variety of answers. What were you expecting, everyone to say "yup, the world's full of cunts"? Well, here you go: the world is full of cunts. But even the nicest, most well-meaning person out there will, at some point, do something, completely inadvertently, that leads them to appear selfish in the eyes of others. And you know what? They won't even know they've done it.