When casually speaking English I use the word "actually" a lot at the beginning of a sentance, or as part of the flow of my speech. e.g.
Actually, next semester doesn't start for a month.
Actually, I don't have any siblings.
I would like to be able to continue this speech habit in Mandarin Chinese, I have been using 事实上 (shìshíshàng), but from my listeners' reactions I am not sure if this is really the same.
What is the closest equivalent expression?
"其实" or "其实呢" is more similar to what you wanted, casually. E.g.
其实我没有兄弟姐妹.
"事实上" is not wrong, but it is literally "in fact" or "as a matter of fact".
Following on from Flake, I also often hear people saying 那么 (那) or just as a way to begin sentences, or 那个 when stopping to think in mid sentences. Is that the sort of thing you mean?
An addition to other great answers:
反正 can be used as "actually" too sometimes.
Example:
- 谢谢你过来帮我 (Thanks for coming over to help me)
Xièxie nǐ guò lái bāng wǒ- 反正我刚好在这边附近而已 (Actually, I happened to be just around the corner)
fǎn zhèng wǒ gāng hăo zài zhè biān fù jìn ér yǐ
