Why do these situations happen to me?

I wrote about the band director not too long ago.

I failed to mention that this awkward situation came on the heels of two other incidents on the same day that had "worked me up."

I don't even remember now what the first one was, but the second one was when N and I were on our way to field hockey in traffic, stopped at a light. A man in a white truck next to me waved for me to pull forward. When I rolled down my window to see what he needed, he informed me that I needed to pull up closer to the car in front of me to allow more people into the lane.

I told N, "I think he just mansplained driving to me."

Sometimes I can come across as a complete bitch, and I hate to even say that word because what I'm actually coming across as is a woman who is assertive when things are stupid. A woman who doesn't just sit there and allow stuff to happen around her but speaks the truth/common sense when it needs to be spoken. 

Like telling the band director the cones weren't up so how could I possibly mindread and know his plans for band when they weren't practicing outside when I parked. 

Yesterday, something fury-inducing happened.

I went to D's work clinic to pick up a prescription, but the pharmacy had failed to deliver it to the clinic (as they were supposed to). The clinic nurse called them, and they said they had it.
So, I went to pick it up from the pharmacy.

Let's be very clear and specific here: The pharmacy screwed up so I drove from where I was supposed to pick it up to the second place.

When I got to the pharmacy and asked for it, they said they didn't have it and I'd have to get it the following day.

It was at this point that something resembling smoke came out my ears.

And so I got on my phone and called the clinic. I spoke to the clinic nurse (whom I had just seen seven minutes prior) and asked her who at the pharmacy she had spoken to that told her the prescription was ready.

This individual then went to the back of the store (where the original girl had gone and found nothing) and found G's prescription, which was there, but still wasn't ready to go out the door.

It had been called in at 9:30 am; it was now 3:30 pm.

I didn't call anyone names.
I didn't tell them they are stupid or inept.
I didn't cuss anyone out.
But I said in an assertive voice, "Wait, a minute. Brittany just told the clinic nurse that the prescription is ready, and you're telling me it isn't ready? I need to talk to somebody in charge who knows what is going on because I drove over here to pick up the prescription that you failed to deliver in the first place."

I spent a considerable part of last night fretting over whether I came across as a bitch.
Do I come across this way all the time?
Are my hormones and general mood instability coinciding to make me a raving banshee?

Of course, I'm biased, but I don't think I'm a lunatic.
I think most people think I'm pretty nice (although admittedly my filter is a little messed up).
Because I don't insult people in general.
I try to be fair-minded and considerate.

I simply won't just "take it" if it is poor service that I'm paying for or someone accusing me of doing something that I didn't do or blaming me for something I am incapable of doing (like mindreading).