How is my data stationary? 
I did a quick Dickey-Fuller test, to test whether my time series is stationary, and the result gives a P value of 9.6*10^-15, or in other words stationary.
How is this possible, my data clearly doesn't seem sttionary. The mean seems to be constant(to an extent), no seasonality issue but it's the variance?

The ADF test has a null hypothesis of presence of a unit root. Clearly, your series does not appear to have a unit root, and the ADF correctly rejects $H_0$. However, absence of a unit root does not imply stationarity. Consequently, rejection of $H_0$ with an ADF test does not imply stationarity. How so?
Absence of a unit root is a necessary but not a sufficient condition for stationarity. Time-varying variance is one characteristic of nonstationarity, and it applies to your case. The ADF test is not designed to capture that, however, so no wonder the results are what they are.
