YOU SAID:
i have a really bad headache
INTO JAPANESE
私は本当にひどい頭痛がします
BACK INTO ENGLISH
I have a really bad headache
INTO JAPANESE
頭痛がひどい
BACK INTO ENGLISH
Severe headache
INTO JAPANESE
激しい頭痛
BACK INTO ENGLISH
Exertional headache
INTO JAPANESE
激しい頭痛
BACK INTO ENGLISH
Exertional headache
That didn't even make that much sense in English.