You are now 37weeks so avoiding symptoms might risk your pregnancy
. You have to see a doctor personally when you develop any new complaints at this stage.
Headache which is severe along with nausea
and some brown sputum should be brought to attention. These symptoms can developed in raised blood pressure which can also present with blurring of vision, swelling over body and convulsions. You would manifest only when the Blood pressure is very high and these can be warning signs of raised Blood pressure. Before you land into disastrous complications you should see a doctor.
You got yourself examined at 37weeks. It is quite possible that your labour has progressed since you have cramping an increased nausea which is also seen in labour.