Sometimes (like once or twice a week) it happens to me that I feel really bloated. It feels like my belly wants to explode, and I feel really unconfortable and can't stand up straight because of the pain associated... It usually happens at night (eg. it started at around 9 pm today..)
Is it normal? Does it happen to other people? What is the cause? Any solution?

It sounds like intestinal issues which may be caused by too much sugar or sugar substitues or carbs or other gas making materials - even fiber. It could also be your gall bladder or your appendix. It is something you should talk to a doctor about. You might look over your food log to see if you can associate the discomfort with something in your diet.