you might try masturbating or have your partner give you a hand job and get yourself turned on sufficiently so that you will come faster during fucking.
The space behind your testicles relates to indirect prostate stimulation which is the same thing as a woman's G spot which is analogous to your prostate gland.
This is due to your super fast masturbation sessions in the past & healing will be training yourself to sustain higher levels of arousal with new patterns of touching your penis.