Having sex with your girlfriend, why does it get soft right after entering when it was hard before?

Patient's question:

Patient Gender: Female
Patient Age: 27
Hello, you have a condition where your penis cannot erect, or the erection is not firm, or it is firm but short-lasting, making it unable to engage in sexual intercourse. The above conditions fall under the category of impotence. You should go to the hospital to rule out whether it is impotence or phimosis.

Doctor's answer:

Hello, if you have difficulty achieving or maintaining an erection, or if your erection is firm but brief, making sexual intercourse impossible, this may be a symptom of erectile dysfunction. The above conditions fall under the category of erectile dysfunction. It is recommended that you visit a hospital to rule out whether it is due to erectile dysfunction or phimosis. If phimosis is present, surgical treatment should be considered as soon as possible.