hey there. i was academically dismissed from my university last semester due to similar circumstances, so i truly do feel for you. if it's alright, i have a few questions (just so that i can get a better handle on your current situation and try to help):
1. how's your overall gpa? are all of your grades below a 2.0 average or did you only fail this one class?
2. has your university officially dismissed you yet?
3. if you have been dismissed, were you given the option to submit an appeal?
4. how much time do you have left before the quarter/semester/year ends?
5. does your university have a counseling center? (i'll elaborate on this in a minute because i know firsthand that most university counseling centers suck.)
if you're only failing in this one class, email your professor or visit them during office hours. explain your situation. tell the truth about what happened before and during the presentation, tell them you drank to try and rid yourself of the nerves and tell them you have anxiety. be completely up-front and honest. you won't get in more trouble; they'll be glad you told the truth. it'll also prove that you were genuinely terrified of giving that presentation and they'll want to help you.
if you're failing in all of your classes, try and schedule a meeting with the dean (or someone else high up) or your academic advisor (if your school's student services department assigned you one) and talk to them about your fear of failing. believe it or not, most colleges are actually very accommodating toward students who recognize that they can get kicked out and want to prevent that from happening. they appreciate that you're determined to stay a part of their student body and will try to work with you. not going to the dean nor my academic advisor was the biggest mistake i made. i thought i could deal with all my problems on my own; i didn't even let my parents or friends help me. now, looking back, i was my own worst enemy.
please take initiative if you haven't been dismissed yet. there's always time. if you have been dismissed and have the option to submit an appeal, do it and write like your life depends on it. i submitted an appeal and while they would've accepted me on the grounds that i was severely mentally ill, i just wasn't academically competent (my overall gpa way below a 2.0 for the semester). most schools are very lenient when it comes to letting their own kids back in. they don't want to go through the hassle of finding someone new to take your place. they hate having to keep track of a student moving out, giving back their keys, etc. it's a shit-ton of work for them. if your overall gpa is below a 2.0, though, they will begrudgingly go through with it. this is mostly because they can't let back dismissed students who mathematically cannot achieve an accumulated yearly gpa of at least a 2.0 (because if you get less than a 2.0 for the year, you're permanently dismissed).
anyway, here's the point i was trying to make about the counseling center: they know people. if you're struggling with anxiety this terribly, go there. like other mental health facilities, they'll do a consultation, evaluate you and move on from there. generally speaking, if they can't help you, they'll point you in the direction of someone who will. i obviously don't know where you go to college but if you're close to a larger town at the very least, they will tell you where you can find more professional help in said larger-town-at-the-very-least so that you can find and get the help you're seeking.
sorry that this turned into such an essay! i have a little too much knowledge on this subject after dealing with it firsthand. i just want you to know all the options you have before it's too late because you're right: flunking out is the absolute worst. please fight for this and don't make the same mistakes as i did.