Mostly likely nothing as bad as the cancer so see your gp and get peace of mind. You sound a bit run down so I would suggest taking Vitamin C daily. Remember, today's foods only have half the nutrients they did 100 years ago and I think the Vitamin C might be one of those we just don't get enough of nowadays.
BTW partners don't get a vote. Mine told me the same thing for 6 months before I finally went against him and saw the doc for the original cancer diagnosis. I had just spent 3 years (physically myself) renovating a 1904 house, putting in floors, walls and ceilings as well as tiling, painting, putting in new window frames, the lot. I was very fit then. Hubby got used to running a house day to day himself at that time with cleaning things so it put him in good stead to be my carer when I got the cancer.