What does it mean if a guy starts to struggle to orgasm during sex? but is fine with finishing during masturbation?

Unlikely organic: Frequently in one's sex life,these occurences are normal & unlikely due to a significant physiological pblm requiring in depth medical workup for erectile dysfunction).That said if this persists a PCP should eval for thyroid,EtOh use & med effects etc.In the interim,practice makes perfect & often when men are engaged in sex a long time or several times in short time ejaculation can weaken. Safety