Why am I so nervous and anxious when I speak another language? :(?

I understand that I of course I will not be able to speak it at ease and so fluently when it isn't my first language but I read a lot and listen to english music A LOT and in my head i speak perfectly..but when I am in front of ppl I start to stutter and focus on trying so hard not to..which results to forgetting the right words and I end up sounding like an 8 year old :( I swear when I type I seem much more mature but when I speak I sound like im a retard or illiterate..its frustrating me because im none. And I've been told this by a lot of ppl. ugh.. how do I get over this phobia??