Forget university, you need to fix how you approach life. I know what I say here is going to sound harsh, but let's be real here, none of your family or friends are going to tell you this (or maybe they have). Get your shit together. You're on uni break now so I'd do the following:
1. GET A JOB! This is so you don't have to rely on Centrelink payments and have a bit more flexibility in your life. Even if that means walking into every place nearby, Woolworths, Coles, some random fish and chip shop etc. You'll need it for developing a resume and it will allow you to become more social and fix your isolation problem. Yes, some places are going to reject you, but you need to be okay with that. I don't know what you do everyday, but get up early, shower, wear something clean and walk into at least 10 places and ask if they are hiring. As someone who currently works at Woolworths, we mainly hire online, however, I've known some people who literally walked in and asked for the Store manager, introduced themselves, and said they will take any position. Funnily enough, they got a job within a few days.
2. Defer from your course. You clearly don't care about engineering so why keep doing it. Is it because you think engineers get paid well? No offence, no one will want to hire someone who has 8 fails on their transcript unless they have proven themselves in the industry already or know someone within the company. Take it from me, I did a Bachelor of Accounting and did next to nothing for the duration of my degree (essentially relied on Year 12 knowledge), failed 5 subjects and had a WAM around 61 by the end of it. I went to 16 interviews, most of them requiring a phone call interview and then two face-to-face interviews and no one would hire me, because there was always someone better than me. So basically I've sat through 48 hours worth of interviews and never received a job. I even asked why they all rejected me, most would tell me to keep doing what I was doing (and sort of felt sorry for me) whilst others straight out told me my marks were really bad. But that hasn't deterred me, I'm still applying and I even went to interview workshops at Deakin (I'm doing my masters there at the moment to get a higher WAM). Bottom line, I'm doing something to fix it.
3. Start meditating everyday and work up to 20 minutes. I assume you have a smart phone, download an app called, 'Calm', it's free, choose a guided meditation and do it everyday. This is the best form of medicine for any mental health problems you may have, as I'm going to assume you don't have a chemical imbalance which requires a prescription from the doctor, but rather you are just feeling depressed because of how everything in your life is turning out. Doing this will allow your brain to stop talking and you will feel amazing afterwards. This will also help remedy how you approach life and could potentially fix your relationship or realise it's a bad one allowing you to move on.
4. Start exercising. Whether that's running, cycling, lifting weights. Do something which requires heavy breathing. I don't know many people, actually I don't know anyone, who after doing some decent recreational exercise feels depressed. Unless you were trying to hit a PB and didn't get it. Lifting weights is a very good idea and I can never recommend it enough to anyone with social anxiety or lack of self-esteem. I've trained consistently for over 5 years and it's dramatically improved my life. I am much more confident, I'm not afraid to speak to people, and overall it just makes you feel good.
5. Find a way to ignite some motivation. Personally I watch Gary Vee videos because he has a no bullshit policy to finding success. I assume you can apply yourself because you needed a fairly decent ATAR to get into Engineering at Monash, so try and look for some passion and drive again. Don't let life screw you over. No one likes someone who is helpless. Instead, be the person who works their ass off and gives everything 100%, and even if you fail 50 times, people will admire your persistence, because a lot of people are quitters and it's a real turn-off.
But getting back to university, the day you start your degree is the day you start your career. So before you start any sort of degree again, think about whether or not you actually want to do it. If you hesitate one bit. University isn't for you! Based on what I read from you, in that you aren't motivated to sit an exam, answers that question already.