Matheus, you're pretty good man. I can tell from your writing that you have a pretty high understanding of english. You know your weakness already so I wont harp on that. But I bet that after you get over your fear of speaking in english, you'll progress a lot quicker than you think because you already know most of the words, grammar, and information. You just have to get the courage to say something. After that its just a matter of saying more (in your case). 

Lack of Confidence.

Well, I've been self-teaching English for about 10 years now but I still don't feel comfortable speaking with friends or using it professionally. I have one American friend who speaks Portuguese really well and every time I'm talking to him I always use Portuguese instead of improving my English skills. He told me my English is good, but I'm not that confident for some reason that I can't explain. I've been watching videos and movies only in English for 2 years and even though I can understand everything I'm watching I still don't feel like I could talk freely. Probably because I live in the countryside of Brazil and there aren't many foreigners to talk to could be the reason why I don't practice my skills, or it's just a fear of failure. But no matter which reason it is, I have to talk or I'll never be able to speak as fluently as I want to. The funny part is, I can sing in English, and love rap, sometimes even change the lyrics to fit my spirit or because I think another word would fit better in that sentence, vocabulary is not a huge problem for me (I need to learn more and more everyday, for sure, but I can survive easily in an English speaking country), the problem is always lack of confidence. Maybe someday I'll get over it and just let myself make some mistakes for the sake of improvement.