Could be hormonal. Have you seen an endocrinologist? Sometimes the tests for thyroid can be wrong. Could also be a change in medication taken recently, loss of muscle mass, or increase in the stress hormone as you age. If you are approaching 40, you might want to make sure that you have a protein snack around 2:30 in the afternoon. Stress hormone levels are highest from 4 p.m. to 9 p.m., and eating too much carbohydrates during that time increases weight. Too much cardio can make muscle mass decrease, and cause weight gain. (I didnt know that until my doctor told me to up my weight training and reduce cardio) I would see my GP and see a specialist if you are concerned. There are great appetite suppressants available by prescription if you are also in need of that. Hope that helps.
maybe your ust gettting older, there can be a million factors and you didnt give enuff detail. If you work out offten and lsot weight then stop losing weight you may have just hit a platue. There isn t going to be a sickness that will stop u from losing weight, its all the same make sure your calorie intake is low, you calorie burned is high, and keep you matabolism up. your not losing weight bc of something your doing differently, of perhaps you just reached your natural weight.
One of two things. Either your doing something wrong (not going to give you advise, you said you dont want any :D ) or the weight you have is denser than normal, causing it not to go away nearly as quick, and usually to get kinda tighter the more you work out.