For three months now I have not seen my periods. I took 4 pregnancy test they all negative. But the problem is I am still not on my periods! What is wrong with me, or do pregnancy test lie?

Go to a doctor, they may be able to explain why you haven't gotten your period

When did you take the four pregnancy tests? The levels of hormone that the home tests detect drop off after the first couple of months. If you want to be sure, get a blood test.

There are reasons other than pregnancy why you might miss a period (although three is a lot): weight loss or gain, prolonged stress, age (some very young women have extremely irregular periods while women approaching/beginning menopause may skip periods), birth control pills, etc. Anything like that going on?

There are many reasons for missing a period, Your age, stress, other illness can all be issues.
Also false negatives is common, esp if not used first thing in the morning upon waking.

I agree time to visit your doctor for an exam