Post-sex crash: semen loss vs. dopamine withdrawal (vs bonding withdrawal?)

I had sex on the weekend for the first time in 3 months. I usually sleep alone and keep to myself, but this weekend I spent 24 hours connecting with someone very closely. No P or M but I O'd 4 times, each time losing lots of semen. Two days later I'm feeling a sharp crash in my mood. I'm depressed and pessimistic and self-doubt it creeping in a lot. This usually happens to me in the week after sex.

Why does this crash happen after sex? Is it the loss of semen b/c of ejaculation? Is it the dopamine hit b/c of orgasm? Is it bonding chemicals in my body like oxytocin b/c of the intense closeness? I know all these probably play a role, but how important is each one?

I'm asking b/c I want to go on a semen retention challenge for 90 days (or more) but I still want to have sex. I'm considering non-ejaculatory sex (like kareeza and Taoist bedroom arts) that leads to orgasm while retaining semen. Should I still expect a crash in my mood after non-ejaculatory sex? i.e. because of the effects of dopamine, oxytocin, etc (which would still be there b/c of orgasm and bonding). How important is semen retention compared to these other factors?