Frequently and multiple times during the day, you will note fluctuations likely due to fluid, you lose it by sweating and urinating.
If you must, plot it in a diary or graph, for a month. It is steady, sustainable loss that is unexplained that causes alarm. At your weight, dropping 7 punds without trying or dieting may be worth a visit. Cancer
in a 22 yo is not high on my list of worries for u.