First off, I'm not going to publicly admit the things I've done but if that makes you stupid I don't know how I function.
Secondly, is English your first language? Don't take this offensively it's a serious question.
Thirdly, you don't sound stupid you sound remorseful and you sound like you have a confidence problem. You're 18, you graduated high school, life is good! Cheer up buddy!!
the EMT curriculum is taught at the HS level, some may argue the paramedic class is as well, I don't think it is, maybe some of the books are rated at that level and some kids can retain that information in that format but that's a different topics.
I'm going to tell you this:
You can do anything you set your mind to, what matters is your drive and your want to do it. There are some people out there that are far from brilliant who have done some brilliant things. There are resources out there to help you through class. Classmates, teachers, tutors if you're at a CC, hell get a job as a vehicle supply tech at the local ambulance company and you'll make friends that can help you study. You just have to want it to make it happen. You're reaching out to us...you're smart enough to think to talk to people in the field before you start doing something. Generally a good idea.