Nagging injury not certain what to do about it

Have a recurring inner thigh/groin injury on my right side that waxes and wanes with use. It was rested all winter but I'm nervous about going into my second year of running with an easy-to-injure sore point. Doctor was no help - rest ice nsaids etc. No evidence of hernia. Last year I did maybe a 250 mile summer and this year I'm hoping to do 500. Looking for advice, particularly if it's from middle aged men with the same injury. I am willing to stretch etc but nothing I've tried in general stretching and yoga doesn't seem to help. Our snow has melted and I'm raring to go but very nervous and looking for some tips for a novice later in life runner. It sidelined me for about 6 weeks at the end of last summer and I don't want that to be a cycle this year.