Hi ESL teachers,

I'm a junior college student studying in the U.S. English is my second language, which I started learning since the 1st grade in bilingual approach. However, I didn't have much English speaking practice before I came to the U.S. Since I've had a longer experience of writing English essays, I'm more satisfied with my written English skill than my speaking skill.
Even though I can write in English very smoothly and quite expressively, I'm finding myself not being able to sustain a high oral English proficiency. Some weeks, I can speak naturally at a high proficiency level. But some weeks, I find myself having to make extra effort to have English words come out of my mouth in a logical and grammatically-correct form. This current week is one of those 'bad' weeks for me. In those bad weeks, even though I know what I want to say and it would come out without any trouble if I write, I find sort of difficult to make up sentences orally. (I don't have any speech disability, by the way. I don't have any problem with speaking my native language.)
A few people I talked to suggested that it can happen when I'm under stress or too tired. I agree with that. I think it's probably a combination of stress and a short amount of speaking practice I had that I can't maintain a consistent oral English proficiency.
But I'm wondering if there are any specific things that I can do to overcome this inconsistency? I'm not sure if this happens only to me or other ESL speakers, too. But if you have any advice or ideas, please please share with me. I would greatly appreciate your help!
Thank you.