What Causes Feeling Of Being Drained Out After Ejaculation?

I am a 45 years old, have been masturbating excessively about 5 to 7 times per week since i was 20. Throughou my childhood until teenager, due to from poor family i ate only abt 5 eggs per week, and beef abt once in 2 weeks. Due to my poor diet, i am slim with little body/muscle mass. Everytime after ejaculating thru masturbation, i felt my muscle especially on the stomach area becomes softer, seemed like muscle breakdown or they are not like holding together. It also seemed that ejaculation seemed to drain out some components out of the muscles. What was actually that and why was that happened. i am sure it was some nutrients drained out. Thank u