How is this a fugue?

I am not hearing fugal form in this piece at all. I do not hear a subject entering in all of the voices in succession. I don't even hear anything that could be recognized as a definite subject. This sounds like you just through-composed a melody with some harmony. Forgive me if this is just going over my head or something (Bachs fugues often do, but I can at least recognize them as a fugue), but it seems like you do not know what you are doing.

Fugues work like this: A main melody (called the subject) begins the piece. After this, the subject is stated again in another voice, but transposed to the dominant key, while the other voice continues to play a contrapuntal line that accompanies the melody. After this, the subject enters yet again, in another voice, often in the tonic key. This continues until every voice has stated the subject one time. This is called the 'exposition' (it is called that because it 'exposes' the material that makes up the fugue). At this point, a new section called the 'development' begins. This section is a free-for-all. You can do whatever you want, so long as you are playing with the subject (the main melody of the fugue). You can play the subject backwards, you can play it upside down, you can play it in other keys, you can make it longer, shorter, you can remove notes or add them, or any combination that you want! The only 'rules' in the development are the rules of good taste (and that the subject constantly reoccurs in one way or another). When thi section finishes, you can add a new exposition, a new development, or you can simply finish the piece. It's up to your imagination at this point. Just don't stop playing the subject. That's the only rule. If you break that rule it is not a fugue. It might be a good piece of music, but it is not a fugue.

It should be noted that the 'goal' of a fugue is to repeat a melody as many times as possible without ever repeating it exactly the same way. Fugues are incredible because they are both strict and free at the same time. If you want to learn more about fugues, you can study all 48 of Bachs fugues from the well tempered clavier at the following website:
http://janus.ucc.nau.edu/tas3/wtc.htm l

That website is an incredible resource. If you are interested in fugues you will be doing yourself a disservice if you do not make use of this resource. I hope you enjoy that website and learn something too.

One final suggestion. Even though fugues are awesome, they are extremely advanced. I suggest you write simpler pieces for many years and study harmony and counterpoint thoroughly before you try writing a fugue. It is nigh impossible to write a quality fugue without studying these things first unless you are a genius.

Good luck and keep composing!