What Is This Discharge With Erected Penis ?

Recently due to my work schedule, I did not indulge in any form of sexual activity (No sex with my wife nor masturbation) for almost 2 months. Till date I never have experienced night emission / wet dreams. However, last night I had different experience. I had a strong urge to urinate while deep in sleep and before I could wake up, I felt wet in my boxers (I wear only boxers while sleeping). I found that my penis was strong and hard. Moreover, my boxers were wet and sticky. It was wet due to colorless sticky fluid like lubrication fluid (pre-cum). The quantity was more and it was not urine. It was not similar to the ejaculation I get while having sex or masturbation. To be frank with you, it was amazing experience and I felt very nice to touch my erect penis. What was this experience? I am 41 year old male.