Strange problem with male reproductive system

I'm 28 years old and I have this problem for about an year now. Often I have a strange sensation as I'm about to ejaculate. It happens without any sexual arousal, stimulation and even without erection. Sometimes it lasts just for a few seconds and fades away pretty easily, but sometimes it's very intensive and I hardly hold myself not to ejaculate. Any ideas what can cause this? I've been posting on different forums in my country, but my posts remain unanswered... From what I read on the internet these could be potential reasons: anxiety, problems with the lower part of my spine, or problems with the prostate... I don't exclude any of these reasons, but I'd like to hear a professional opinion on what could cause these sensations before giving more information, if possible.