Do you mean when you speak to English speaking people not from your background? Sometimes when we hear an accent that is different to ours we get a little confused or afraid/nervous to make mistakes when speaking. I use to feel the same before moving to Australia. When I speak with native speakers with an accent different to mine, I become very cautious not to make mistakes more so for fear of embarrassing myself. It takes a while, but you can watch lots of foreign news and shows so you are exposed to different accents and get your listening skills up. Eventually you will also speak similarly to what you hear. And lots of practice helps you build your confidence too.

Try memorising and practising prose or poetry, as if you were to present it to an audience. You could write your own, quote a book or get some off the internet. Monty Python acts are always a good choice. To begin with rehearse and then say script in front of a native speaker. Once your confidence improves, you can try speakimg normally.

This is due to a nervous personality of course. I guess practising and practising can help you reduce this trouble. You have to find someone to communicate with, who you trust and who can help you practise regularly your oral English. Good luck ! Greetings from France !

Since you are proficient in English both written and verbal, try to speak in English with your friends or family members who know English. Try to make whole sentences in mind before you speak out, practice to pronounce and be confident.

I think you have to work hard so as to avoid entering some subjects that make you feel nervous,and then you can find some friends to help,i think it will be good...have agood luck