It does indeed sound like it is caused from pressure on the prostate. The prostate is filled with many nerves and is believed to be connected to the female G-spot. So as to say, they are possibly related in an evolutionary or fetal development sense. Such as the clitoris and penis, or the labia and scrotum.
It is possible to achieve ejaculation and orgasm through prostate stimulation without any penile stimulation. It also possible to have orgasm without ejaculation, and there isn't even a need for an erection.
Whether it is a problem or not, I would not know, only a doctor could tell you that.
Perhaps from your ease of achieving orgasm through prostate stimulation, you would be a likely candidate for success with devices sold by High Island Health or Aneros. They're prostate massagers designed for prostate health through massage. A most fortunate side effect is extreme pleasure, super orgasms, multiple orgasms, etc. Of course, I mention these not for treating anything. I only brought it up because you seem to be able to easily achieve prostate orgasms.