I get loose motion and stomach upset whenever I eat watermelon. Why does this happen?

Hello doctor,

Yesterday during lunch, I ate drumstick leaves curry. Whenever I eat that, in an hour or two, I go to the toilet (little loose stools) two times. Is this normal? Yesterday I had the same, further after about 5 hours, I ate grapes. After an hour, I had to go to the toilet often (loose motion). Why does this happen? Did I eat anything in the wrong combination? I also get loose motion and stomach upset whenever I eat watermelon after food, especially it becomes severe and affects for two days. Am I sensitive to any such components? I understand that eating fruits after food can cause indigestion, but my friends seem to be not affected, even if they eat a lot of melon after lunch.

Thank you for your quick clarification.

I am 32 years old. I did not have a fever and a rash. Can you please share more on how allergy sensitivity test is conducted? When do I take these tablets, twice a day means morning and night after food? I have planned to drive tomorrow (6 hours). Is it advisable? Now should I restrict myself on any type of easy digesting food? If yes, can you please suggest some? Is it advisable to eat roti? Also, is it normal, that people have such allergies to some foods? Is it possible to correct it than trying to avoid it (as sometimes, knowingly it may not be avoidable or unknowingly we might consume)?