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?

I would agree you have visual evidence the series as non-stationary variance, and would suggest the unit root test that drives the ADF test does not detect this. While the ADF is great for testing trend stationarity, you can justify using your own discretion here on whether the variance is stationary.
There is also the possibility your version of the ADF test doesnt detect variance stationarity. From the ADF Wikipedia page:

The alternative hypothesis is different depending on which version of the test is used, but is usually stationarity or trend-stationarity.

There is a good Stack Overflow: Cross Validated post about the versions of the ADF test
