Hi, Welcome to HealthcareMagic Forum.
You are suffering from nothing but Nightfalls. It is absolutely normal to experience this if you don't have sex for quiet a long time as excess semen builds up and gets collected, since you are a mature adult. Not to worry, as it wont have any serious repercussions on your health and your sex life. If you don't want them to happen, you may want to have Sex regularly or masturbate. This will release the excess ejaculate which had builded up over time and you wont have nightfalls.
is not related to having sex or nightfalls, it is related to doing some repeated strenuous work. Get adequate rest and eat healthy nutritious balanced diet which should include fresh fruits and green leafy vegetables.