I’m pretty sure the semen stays in your body I’ve read before though that sexual fantasizing results in a loss of energy so you lose internal energy, but not semen
That's a crazy insight because I never thought they were separate like that before but it's true. Lusting is pleasurable and a vice so I automatically considered it to be non energy draining for some reason and thought it was the mere loss of semen that accounted for the tiredness. Loss of semen causes the stupidity, lusting causes the drained energy... the two go hand in hand but are necessarily tied at the hip.
The problem with fantasy is that it leads to edging and masturbation, which leads to porn. For me all the above are so linked in my experience, it's hard not to go there. Plus, once aroused, those hormones will keep me up at night, which is a further temptation and drain on my body and mind.
When I retain over a certain amount of time I'll see semen in my urine (toilet) without edging. Just waking up.
Yes, it is. Sperm cells and semen are stored separately in the body. When you fantasise your body prepares itself for sex and so they get mixed together, then if it isn't ejaculated they are lost through the urine or via wet dream.