I know it is easy said 'don't be afraid', you better try to know why you are feeling so in the first place.
Probably you need some self-confidence boost.We are all learning languages and are indeed making lots of mistakes, so it is not only you that don't find the words,it is a natural process and you should be gradually improving and progressing towards higher degrees of influency.
So don't let these feelings block your ability to understand ,listen attentively and ask your teacher or the foreigners you talk to about the meanings of new words or expressions.
I will give you some hints here as how to improve your oral English ,what you should do at the same time :
Observe the mouth movements of those who speak English well and try to imitate them.
When you are watching television, observe the mouth movements of the speakers. Repeat what they are saying, while imitating the intonation and rhythm of their speech.
* Until you learn the correct intonation and rhythm of English, slow your speech down.
If you speak too quickly, and with the wrong intonation and rhythm, native speakers will have a hard time understanding you.
Don't worry about your listener getting impatient with your slow speech -- it is more important that everything you say be understood.
* Listen to the 'music' of English.
Do not use the 'music' of your native language when you speak English. Each language has its own way of 'singing'.
* Use the dictionary.
Try and familiarize yourself with the phonetic symbols of your dictionary. Look up the correct pronunciation of words that are hard for you to say.