<human>: Condense the text into a few key points

Firstly, sorry for the grammar, English is not my first language. 

I truly loved my fiancé. I thought she is the only one. 

I was helping her with everything. Her postgrad studies, spending several hours every day to explain to her some concepts. I have written the largest part of her dissertation. Whenever she was sick, I walked her into a hospital. I was happy to follow every whim of her.

Every week or two I wrote a poem and bought her beautiful flowers or jewelry. She seemed truly happy with me. 

Six weeks ago my mother was violently murdered by group of criminals. They took her money and buried her body. I am currently going through a really dark depression. My fiancé was supporting me.

Three weeks ago, after finishing her studies, my fiancé has returned to home and after some time she traveled with her mother to another country for about a week. I was in different city, finishing my job. She has returned 3 days ago and I noticed that almost everything she told me about her travel was a lie. After really heated discussion she has admitted cheating on me with some guy from the same hotel, she met that night in a nightclub. She wasn't drunk by the way.

Now I am slowly going mad, because my heart still loves her, but my head saying that she is a monster doing this to me in such circumstances.
<bot>: My fiancé had one night stand with a guy she met at nightclub while I was grieving for loss of my mother. I am going mad because I still love my fiancé.