i `ve got the same problem , i know alot of words and idioms but when it gets to making up a sentence its seems allitle bit confusing thinking 2 times befor making a complete sentence and when u just do it start saying to urself OMG ! I should `ve said ... instead of .. It gets me crazy :(

Keep trying lady... You are doing an excellent job. Remember that learning a new language is a test of endurance. A usual practice that helps me to overcome some obstacles related to my speaking is to speak alone with myself. For instance, I try to explain to myself situations in the past if I want to practice my speech in past. It is also useful to talk to yourself before talking to someone and practice what you are going to say in that situation. You could guess what kind of question you will make and what kind of question the other person might have regarding that conversation. I hope this suggestion can help you.

One thing you can do is, you should speak to as many people as possible. May be through skype or direct in person. Speaking helps in improving confidence. Once you are confident, words will start flowing. When you are grammar concious you tend to forget words. So I would suggest you to just speak irrespective of grammatical mistakes. Also make notes when you realize that you have made a mistake. Next time don't repeat it. I hope this suggestion shall help you.