This is not frequent change of glasses ,it's slight subjective variation .which is quite possible.
There may be 3 reasons of your problem
1..stress and anxiety
2..lack of proper centration and axi2 in specs
3..if you are a regular computer user then you are likely to have computer vision syndrome. And if associated with migraine then both complement each other and over and above anxiety,aggravates the problem .
Next Steps
perform yoga and observe some precautions to prevent development of computer vision syndrome.