My wife hasent had a period for 8 months then recently had light spotting for a few days. Could she be pregnant?

Has her belly gotten bigger? Has she taken a pregnancy test?

I'm pretty sure you would have noticed by now..

There are many causes and combination of causes why a female experiences, "absence of periods" called, amenorrhea. I would think she should have been seen by a doctor months ago to determine the medical cause and have it treated, unless she is pregnant and then she would need pre-natal care which is very important for mother and baby. There have been cases where a woman is pregnant and no normal symptoms of pregnancy and no significant weight gain. During pregnancy a small amount of bleeding, if it happens, is usually normal. She should see a doctor to determine the cause and sooner if she is in pain.


Absence of Periods
The medical term used to describe "absence of periods" is amenorrhea. Women normally do not menstruate before puberty, during pregnancy, and after menopause. If a woman does not get her period when she normally should, it may be the symptom of a treatable medical condition.

There are two types of amenorrhea: primary amenorrhea and secondary amenorrhea. Primary amenorrhea is when a young woman has not had her first period by the age of 16. Secondary amenorrhea is when a woman who has had normal menstrual cycles stops getting her monthly period for three or more months.

What Causes Amenorrhea?
Amenorrhea can be caused by any number of changes in the organs, glands, and hormones involved in menstruation.

Possible causes of primary amenorrhea (when a woman never gets her first period) include:

Failure of the ovaries (female sex organs that hold eggs).
Problems in the central nervous system (brain and spinal cord) or the pituitary gland (a gland in the brain that makes hormones involved in menstruation).
Poorly formed reproductive organs.
In many cases, the cause of primary amenorrhea is not known.

Common causes of secondary amenorrhea (when a woman who has had normal periods stops getting them) include:

Pregnancy
Breast feeding
Stopping the use of birth control
Menopause
Some birth control methods, such as Depo-Provera
Other causes of secondary amenorrhea include:

Stress
Poor nutrition
Depression
Certain drugs
Extreme weight loss
Over-exercising
Ongoing illness
Sudden weight gain or being very overweight (obesity)
Hormonal imbalance due to polycystic ovarian syndrome (PCOS)
Thyroid gland disorders
Tumors on the ovaries or brain (rare)
A woman who has had her uterus or ovaries removed will also stop menstruating.

Link:
Absence of Periods (Amenorrhea): Causes and Treatments (http://www.webmd.com/infertility-and-reproduction/guide/absence-periods)

How old is she, was her periods regular before ? But there are many reasons for this,

I would assume after the second missed period she did all of the pregnancy tests, and why after three or four missed periods has she not went to the doctor