Help! I’m going to need to drop out of Japanese if I can’t start being able to speak

I started learning Japanese when I was 12 in school, I’m 18 now and I’ve been taking it every year since, I’ve always been an A student in Japanese and was top of my class in it in high school, in college though I’m slipping. This is because in high school I was able to write Japanese well and when I spoke it was a presentation that I rehearsed. On a knowledge level, I am at an intermediate level and I understand how to read and writ e, however when I’m speaking I can’t string sentences together, I’ll be like “買います-買いー買う、買う時…” (end goal = 買う時) when trying to string together a basic sentence. The other people in my class know much less Japanese than me but can still speak much more coherently than I can. I was wondering if anyone had any ideas on how to fix this issue because I think I’ll need to quit Japanese if I can’t fix it soon