I am struggling to improve my fourth language

I am 23, I know 3 languages, 2 of them are my native languages, and English. I am fluent in those languages.

1. The problem kinda arises with my fourth one. I use it a lot as I study in it and use it every day. But I have a HUGE problem with actually speaking in it, like holding a conversation and expressing myself. I don't really have a problem with understanding the speakers. I don't wanna degrade myself as I have started learning it only a year and a half ago from scratch, but I also feel so fucking dumb all the time. I thought that living in an environment where everyone speaks that language would help me to improve it much faster. I think I have a fear of speaking in it overall. If there is a chance of switching to English, I do that. One thing that doesn't really help is that my teachers are so demanding and press me to speak during the classes, and I just feel so stupid, and all the words just leave my head. Are there any ways to overcome this fear, or maybe some techniques?

2. Also, if there is a way not to get overwhelmed by the quantity of languages in my head, it would also be nice :( I mix them all the time as I am speaking and using every single one every day, it just messes with my head. I get "slow" sometimes in my answers because of that.