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