Can you take Mucinex during pregnancy? I'm 18 weeks approximately...?

I took Mucinex a little while ago because I woke up with severe chest congestion yesterday and can't breathe. It's a little better today... not so painful, but my body is starting to break up all the flem. I took a Mucinex without even thinking about it... is it okay? First and only time taking it during pregnany... 18 weeks.