Is it grammatically OK to use "Sorry for bothering you"? I often hear "Sorry to bother you".
Right. "Sorry to bother you" is more idiomatic than its other variants.
"I'm sorry to bother you" puts it unquestionably in the present.
I would use "sorry to bother you" at the beginning of a conversation and "sorry for bothering you" at the end of a conversation.
Having said that, there are several other possibilities, such as:
- "I'm sorry to be such a bother.
- "I'm sorry to have bothered you"....etc.