My mensuration cycle mostly 28 days that was due on 4th day of this month
Before two hour ago I discharge little bit spotting but yet menses not arrived.
Now I am having vomiting,and I have unprotected sex from last three weeks conscientiously
I am too much tense please tell me I am pregnant or not?

Maybe just sick at stomach, really too early for pregnancy to have signs.
Also you are not even late, just time for period. No way to even test for at least 2 weeks after you miss period.

Does early spotting means that periods is coming?

Do you really have all this unprotected sex and NOT want to get pregnant?
WHY?
(I agree that it's much too soon to know.)

Early spotting can mean either period or pregnant.
There is not one symptom that determines pregnant or not pregnant!

Does early spotting means that menses is coming?

Yea I am having unprotected sex all the time and I want to get pregnant,
From last week at early morning I am having cramping and also vomitting some times,and I also fell headache mostly time
And also having frequent urination
Please let me tell about pregnancy?

Please read my answer carefully - it answers your question.
ONLY a TEST can tell if a woman is pregnant or just getting her period.

Please tell me about the test?

Home pregnancy test (HPT) can be bought at any drugstore.
They are done starting 2 weeks after period would have started. Plan on buying more if negative.
Spotting can be pregnant or not, no way to know.