Your body is ALWAYS burning fat except for in the presence of constant dietary carbohydrate.

Has your body been burning more fat than when you consumed carbs? Oh yes it is, 100% guaranteed.

Ketosis is for providing fuel to your brain, and yes, after 2 weeks of <50carbs and 48+hr fast, your most definetly IN ketosis.

You go into ketosis as soon as your liver runs out of glycogen (actually before). Your brain needs 120-100 grams of Carbs/day when you started this, and it got it from your liver glycogen+the 50 you ate for two weeks, plus it converted some from fat, plus it brokedown some dietary protein for glucose also.

Over a 4 week timespan, in the absence of dietary carbs, your brain reduces its need for glucose down to 30-40 grams. 20 comes from fat breakdown. The other 20 has to come from ingested (or muscle) protein or carbs, and the 70-90 other grams are replaced with ketone use.

I'd say yes, it sounds like you are. As AnarchyCaveman suggested, Ketostix can confirm if you really feel the need to know - however:

The way I think of it is: though you may or may not be in keto at the current moment, once you've adapted your body to the process of burning fat (ie, passed the "low carb flu" phase), you will notice that you have the metabolic flexibility to do what you damn well please, and nothing will stop you from feeling like a warrior at that point.

If you fast for too long you will gradually decline, though its sort of a gentle settling into a quiet, observant mode (think: sitting in the bushes, hunger knotting your stomach, waiting for anything edible to walk by), rather than a "crash", per se.

For me, this was the phase in which food really began to take a background role in my life. At times I'd even forget to eat, and then I'd refuel, and be on my way. You now have the control; you now have the flexibility to operate without being a slave to your fuel source.

I love that unparalleled focus that comes from long fasting, elevated ghrelin levels, and consuming pure fat (MCTs especially) while already deep into keto. Few things make me feel so animalistic.

Do you use ketostix? You can test your urine for the presene of ketone bodies. I don't do this much anymore, but I did for the first few months of Paleo to try to understand what was working. You can get the test sticks at a pharmacy for about $12 for 50 of them.

If you are feeling great you could be keto adapted - But you probably need to go lower than 50 carbs to do so. My spot is about 20 carbs a day. So yes once you are in Ketosis and you feel comfortable - you are a fatburner - cool hey!

That's a good sign that you're pretty well adapted. You don't need to buy anything or measure exact ketone levels to know that. Depending on your goals, there's a lot to recommend occasional fasting. As Raney implies, it can be hard to maintain regular meals when you don't really need them!