I masturbated about two days ago and then I had a wet dream last night. Could the semen build-up possibly have happened that quickly? It doesn't make sense because I just did this two days ago, so I didn't think this would happen so soon.
The frequency of ejaculations vary by individual, by age, and by circumstances. The average young adult ejaculates twice a week, but it can be as frequently as once a day or as infrequent as once a month. Anywhere in the range is considered normal. Teenagers tend to ejaculate far more often than middle-aged or older men.
Your seminal vesicles typically hold enough semen for two to three ejaculations, even though you can't ejaculate that many times in a row. But this means if your seminal vesicles are particular full, an ejaculation will take down the pressure, but it might not take long for it build back up again.