Mystery foot/ankle pain?

Since I was about 7 or 8 years old I noticed that when I would stand or walk a lot in the day then I would get pain in my feet and ankles. Over the years it’s gotten much worse. I’m 26 and it only takes about an hour of standing or walking for the foot/ankle pain to set in. It feels like a clamp is surrounding my feet, getting tighter and tighter until I’m limping and my feet and ankles swell up. I’ve been to several doctors and had an X-ray. They say nothing is wrong with my bones and that I have plantar fasciitis and that getting cortisone injections and changing my shoes will make it better. Well it’s been years and nothing has helped! I can’t find any information about what is wrong when your entire feet and ankle feel like their being crashed inwards from every direction so please help!?!?! I love to travel and it’s been extremely difficult since with travel there’s always tons of walking. Please help!