SUBREDDIT: r/running
TITLE: Need advice with shoes and blisters!
POST: Sorry if something like this has been posted here recently, I did a few searches but nothing really seemed to answer my question.

I have been running for a while, and have had the same pair of shoes for about 2 years. But every time I run for longer than 6km I get blisters on the insides of both my feet, in a line directly below my big toe. At first I thought it was my running form, but I don't have a heel strike or land on my toes, my socks are also good at ridding moisture as well. 

Could this be a problem with my shoes? These blisters are very painful and I don't know how I've coped with them for 2 years - they're stopping me from running further. If it is a problem with my shoes, how do I get fitted properly? I walked/trotted around the shop when I was trying this pair on for a good 10-15 minutes and suffered no pain.

Thanks for any advice you can give, runnit! :)
TL;DR: 
My shoes give me blisters, not sure why, also not sure what to look for when trying shoes on as these were very comfortable when trying them on in the shop.