I'm just wondering - is this only a problem with speaking English, or do you also have "stage fright" when speaking Spanish?
If it only happens when speaking English, then just be brave and accept you'll make mistakes. Remember that the people you are taking to want to understand you, so they'll help you as well. If they've also learnt a second language, they'll know exactly how you feel.
If it's a general case of stage fright, then the language doesn't matter, Either way, you still need to get used to speaking to (or, in front of) people.
Start with what you are comfortable with and build on that, even if it's only a couple of sentences. No-one's asking for the Gettysburg Address. ;)