Although native-English speakers are always nice enough to tell me that my English is "good enough" to be understood, there are times that I feel uneasy with myself, because I just lack the practice to be able to communicate fluently in English.
Similar feelings here. I am Spanish, and work in Ireland since 4 years ago, so I have to communicate in English.
Even if people had told me quite a lot of times that my English is very good, that they've never have problems understanding me, I still can feel all the extra effort that I have to put into it, as well as being aware of most of the grammar or pronunciation mistakes I do.
Of course, practice is everything. I am clearly way more relaxed now than I used to be. But I still have to take some seconds from time to time to phrase correctly. On the other hand, I do that as well on Spanish. Communicating is hard!
I guess that some Dunning-Krueger effects works here. You are aware of your limitations, even if they are not that big, and that stings.
I have exactly the same problem, a little bit aggravated by the fact that I seem to be a little bit dyslexic and sometimes I type something but I read something completely different.
People tend to be nice, so I just try to get the message through and don't think too much about it :)