We have somewhere you can look up the theoretical dose from the flights you have done. Although it is certainly something to take an interest in, I would be much more concerned about UV exposure as it is something you can mitigate with shades, sunblock, etc. Where you live and the amount of radon in your house is probably more pertinent as well, as it is again able to be reduced/eliminated by physical means.
Skin and lung cancer from the above is definitely a thing, as the stats show. Averaged radiation dose worldwide at 35,000’ I think is ~3μSv/h and that is roughly equivalent to about an 0.00001% increase in the chance of illness per hour, so a 30,000hr career would be 0.3% above baseline which is below the noise floor for general living. Yes it has an effect but probably undetectable.