I am 28 years old. I had a ruptured ovarian cyst. I eat a lot, urinate a lot, and feel sick. My weight has dropped from 54.9 kgs to 52.5 kgs in three weeks. Is sudden weight loss after laparoscopy normal?

NOT NORMAL. Especially that nothing major was found. I would however rule out diabetes in the first place before checking other things. You lost weight, eat a lot a pee a lot. Have your blood sugar examined first. Same time one could look for thyroid function as well. If all these come out normal and the weight loss continues you need a good diagnostician...
You will be fine. You are loosing weight as you are not eating enough due to your temporary illness , once your abdominal condition ( due to rpt. Cyst ) and urinary infection clears you will eat better and gain weight, speak to your doctor.