Peed during orgasm !

Full bladder and alcohol most likely.
Your body shouldn't be able to urinate during orgasm. Climax should should close off your bladder. If you're sure you were having an orgasm?

I wasn't drinking, but yes, I most certainly had a full bladder. I did feel my body readying itself for ejaculation, only the pleasure was quickly cut off by the stream of urine.

Should I be worried about this, or was it just a result of carelessness on my behalf? Because the fact that I managed to urinate so freely while at the peak of erection really worries me!

If you have to go you have to go. Your bladder isn't going to allow itself to explode just because you're erect. It's a little troubling that you lost control of that but unless you see a recurring problem with bladder control I wouldn't let it worry you.