I started rad yesterday and the actual process was uneventful but the aftermath not as I expected. Felt very sleepy coming home and by 2pm had cramps in the bowel. Thought I would have diarrhoea but ...
It does sound like a bug, but if it continuess to happen get it checked. If you were neutropaenic, it wouldn't be related to radiotherapy after only 1-2 sessions. How long since you finished chemo?