why I was tired today

I couldn't (didn't) sleep well last night.
Because I had forgotten to close the windows after cleaning the room.
Then, a lot of bugs came into my room and a mosquito bit me while I was sleeping.
It was really itchy, so I woke up. But, I couldn't find where I was bitten.
Finally when I found it out, it was midnight.

So, I was really tired today.

I was tired today because I didn't sleep well last night. I was cleaning my room yesterday and forgot to close the windows afterward. A mosquito flew in and bit me while I was sleeping, which made me itch. I woke up, but I couldn't find where it had bitten me. By the time I found the bite, it was already midnight. 

why I was tired today

I couldn't sleep well last night.
Because I had forgotten to close the windows after cleaning room.
Then a lot of bugs came into my room and a mosquito bit me while I was sleeping.
It was really itchy, so I woke up. But I couldn't find where I was bitten.
Finally when I found it out, it was mid night.

So I was really tired today