Blood clots on foot sole. Of the feet.

Hi Doctor, I occassionally develop very painful, what appears to look like blood clots, on the bottom of my feet. It's been a long time and the root cause has not yet been found out. This happens a few times a year, suddenly, with intense pain and goes away slowly after 5-6 days on it's own. During that time, I am unable to walk properly/comfortably as it pains a lot for those few days. I am even woken up sometimes due to pain in the middle of the night. I have flat foot condition. Consulted lots of doctors, went for blood sugar, uric acid tests, etc etc, everything is normal. One doctor did mention it can be because of flat foot, but has not confirmed it fully. As per another doctor's instructions, I even tried changing my diet, tried low protein diet, for example, for almost a year, but nothing worked. Attached an image 2 days after the clot, for reference. Affected areas: 1) Mostly the area just at the base of the fingers 2) sides of the feet. Thanks a lot for your time/opinion.