Talk to Urologist on Sexual Sensitivity And Regular Night Fall

I am suffering from intense sexual sensitivity. I get immediate erection even while talking to a girl or with mere thought. I even secrete liquid while talking on text with my fiance. Many times, I get discharged without touching my penis. I am also getting nightfall frequently despite doing masterbuation once in a week or two. After nightfall, I maintain erection for very long time and it's very hard and sometimes little painful. Please explain the reasons so that If this is an issue of concern, I can take medical treatment. Thanks