Why Does My Erection Go Limp After A Few Minutes During Sex, And Could It Be Related To My Acid Reflux And Prostate Medications Or Smoking?

I get a hard on I start making love to my girl my dick goes limp after 2 to 3 minutes I take acid reflux pills in the morning and I take a pill at night before I go to bed for an enlarged prostate and I smoke what can I do to correct this problem it s been happening for about a month now