Hello from JustAnswer.The amount of radiation exposure from a plain chest x-ray is very small. It is about 1% of the radiation exposure from a single chest CT scan. Or to look at it from another perspective, a single set of chest x-rays involves an amount of radiation exposure equivalent to three plane trips from coast to coast in the US, and most people do not hesitate to travel by plane.There is no appreciable risk of cancer incidence from the number of chest x-rays that you have received. We still would rather only perform a chest x-ray, or any x-ray, when it is indicated, but when it is otherwise indicated, there is no reason for concern about the amount of radiation in a plain chest x-ray.As for the cause of the cough, the likelihood of cancer in a 32 year old is very remote. It is much more likely to be an inflammatory condition, either a primary condition within the lung, such as chronic bronchitis, or in response to an irritation of the lungs, such as through acid reflux. It is possible that TB can come back, but if you completed a full course of treatment, the likelihood is low. Several negative TB cultures are reassuring, but does not completely exclude the diagnosis. At the present time, a chest x-ray is an appropriate next step, but it may also require further evaluation, depending upon the findings on the chest x-ray.If I can provide any further information, please let me know.