correction

This morning, as usual, I was waken up by the call from my gf. By habit, I asked for the time and it was 8:30. I was surprised because she usually calls at 7:30 if I overnight at my mom's and the next day is a working day. In fact, the night before I'd reminded her to call at 7:30 just in case she forgot as I hadn't been back to my mom's on weekedays for some time. A no-brainer calculation which took me five seconds confirmed that I'd be late for work as the drive would take two hours compared to one hour from my home.When asked with a suppressed disappointed tone, she slightly raised her voice and told that she had called an hour ago and that was a generous confirmation call which I knew was supposed to be our morning chat while on the road.

Could you please correct any mistakes in the above paragraph and point out any unnatural sentences? Many thanks!