zutuu ga hidoi toki ha, hayame ni nemasu.

Both can talk about a headache, but they are structured differently:

• 頭が痛い = my head hurts
• 頭痛がひどい = the headache is severe

So in this sentence, the speaker is not just saying there is pain in the head, but that the headache itself is bad/intense.

A useful way to think about it:

• 頭 = head
• 頭痛 = headache
• 痛い = painful / hurts
• ひどい = severe / awful / bad

Because 頭痛 is already a noun meaning headache, it makes sense to describe it with ひどい.

Here, が marks 頭痛 as the thing being described.

So:

• 頭痛がひどい = the headache is severe

This is a very common pattern in Japanese:

• Noun + が + adjective
• 雨が強い = the rain is strong
• 風が冷たい = the wind is cold

In this sentence, ひどい is the adjective, and 頭痛が is what is severe.

ひどい often means things like:

• severe
• terrible
• awful
• bad

In 頭痛がひどい, it means the headache is severe or really bad.

It does not mean the speaker is being morally harsh or cruel here, even though ひどい can have that meaning in other contexts. The meaning depends on what it describes.

Examples:

• 風邪がひどい = my cold is bad
• 雨がひどい = the rain is terrible

Both can appear in Japanese, but they do slightly different jobs.

In this sentence:

• 頭痛がひどいときは、早めに寝ます。

ときは means something like:

• when I have a bad headache, ...
• in times when my headache is severe, ...

The は after とき marks the whole time phrase as the topic or condition being discussed.

If you said ひどいときに, that would sound more like simply marking the time at which something happens:

• 頭痛がひどいときに寝ます = I sleep when my headache is severe

That is possible, but ときは is more natural when talking about a habit, general rule, or what one does in that situation.

The は highlights the situation “when the headache is severe” as the topic or condition.

So the sentence is structured like this:

• 頭痛がひどいときは = as for times when my headache is bad / when I have a bad headache
• 早めに寝ます = I go to bed a bit early

This pattern is very common:

• 忙しいときは、外食します。
  • When I’m busy, I eat out.
• 眠いときは、コーヒーを飲みます。
  • When I’m sleepy, I drink coffee.

The は gives the sentence a “speaking generally” feeling.

Not exactly.

• 早く = early / quickly
• 早めに = a little early / earlier than usual / on the early side

So 早めに寝ます means:

• I go to bed a bit earlier than usual
• I turn in relatively early

This is softer and more natural than just 早く寝ます in many cases.

Compare:

• 早く寝ます = I go to bed early
• 早めに寝ます = I go to bed a little earlier than usual

早め is a noun-like form, and に turns it into an adverbial phrase.

So:

• 早め = an early-ish time / the early side
• 早めに = early / a bit earlier than usual

This is similar to other expressions:

• 多めに入れる = add a little extra
• 少なめにする = make it a bit less
• 控えめに話す = speak modestly / reservedly

So 早めに寝ます literally has the sense of sleep/go to bed at an earlier side/time.

Japanese non-past forms often express:

• habitual actions
• general truths
• future actions

Here, 寝ます is describing a habitual response:

• When my headache is bad, I go to bed early.

It is not talking about one specific past event. It is more like a personal rule or usual behavior.

So the non-past form is exactly what you would expect here.

Yes, the subject is omitted, which is very normal in Japanese.

The sentence does not explicitly say:

• 私は = I

But from context, the natural understanding is:

• I go to bed early when my headache is severe.

Japanese often leaves out subjects when they are obvious from context.

So a fuller version could be:

• 私は、頭痛がひどいときは、早めに寝ます。

But in normal speech, 私は is often unnecessary.

Yes. The clause before とき modifies it.

In Japanese, a plain-form clause can come before a noun and describe it. Here:

• 頭痛がひどい = the headache is severe
• とき = time

So together:

• 頭痛がひどいとき = the time when the headache is severe
  or more naturally, when I have a bad headache

This is a very important Japanese pattern:

• 忙しいとき = when busy
• 雨が降るとき = when it rains / when it is about to rain
• 日本に行ったとき = when I went to Japan

Yes, that is a very natural translation.

ときは literally points to the time when, but in English, depending on context, it can sound more natural as:

• When my headache is bad, I go to bed early.
• If I have a bad headache, I go to bed early.

Because the Japanese sentence describes a general pattern, English often uses either when or if.

Yes, that is grammatically correct and natural.

The difference is mainly nuance:

• 早く寝ます = I go to bed early
• 早めに寝ます = I go to bed a bit earlier than usual

So 早めに sounds a little more nuanced and practical, as if the person adjusts their bedtime earlier than normal.

Also, とき and 時 are the same word. Writing it in hiragana or kanji is both fine.

In many contexts, 寝る can mean either:

• to sleep
• to go to bed
• to lie down to sleep

In this sentence, 早めに寝ます is most naturally understood as:

• I go to bed early
• I turn in early

That is because 早めに suggests the timing of bedtime, not just the act of sleeping itself.

So while 寝る literally means sleep, in this kind of sentence English usually prefers go to bed.