Are you a:
Volcano undergoing an explosive eruption?
I feel quite sick, My symptoms indicate death, And with my fever I will be dead by the end of the week:
The violent nature of the eruption may be sickening if a volcano were to be a sentient being. After an eruption, a volcano can be dormant.
I have been puking for days on end:
This may be in reference to the magma and ash released. The eruption may take place over several days.
My hair is a mess:
This may be in reference to the cloud of ash that forms above the volcano that may resemble messy hair.
I feel bloated beyond belief:
An explosive eruption occurs when gas buildup causes pressure that can't be easily released. Again, if a volcano were a sentient being it may feel bloated.
The heat from the magma may be the cause of this. More physiologically, heartburn is caused from acid entering the esophagus, and in a volcano magma travels from under the earth's surface up through the volcano.
This post is based entirely on my limited knowledge of volcanoes, and may contain factually inaccurate claims.