Because this I've never try to speak in english..I speak only portuguese with my partner!!! I'm so shy and nervous that I start to stutter !!

You wouldn't be nervous if your speaking skills were perfect. Therefore enlarge your vocabulary, learn grammar and syntax. Don't aspire to speak fluent. It's OK if you will speak slowly. Also you needn't worry about your accent. I don't want to say that you should ignore the pronunciation rules, but if your accent isn't very heavy, it won't make your speech incomprehensible. More than that I think there is a particular charm in a slowly speech with a light accent. You just have to learn to make your foreign parentage your merit.

You can't. Just keep on speaking.