英语翻译：我因为肚子痛不能来上今天的课,所以想跟你请个假.

I am wondering if I could ask for a leave bacause I have so terrible a stomach that I can not take today's class.

I have a stomach pain today, so I cannot come to school and want to ask for a leave.
这样写就可以了

I won't be able to come to class today because of my stomach ache.So I want to/have to ask you for a sick leave.或者I can't come to class today for I'm having stomach ache.So I want to ask for a sick ...

I cannot attend class because I had a pain in my stomach and I want to ask for a leave.