When I first started uni I was overwhelmed too. I was trying to do too much; Too many classes, a job and other activities like sport. I didn't have time for socialising with friends, so it was very lonely and stressful.
You need to prioritize. Assignments/Assessments that will affect your grades should come before extra work like readings. IF the readings are necessary to complete work then read them, but if they are not essential and you may not need them to do the work, then wait until you have the time to do them. Maybe try finishing off all your assignments for the semester as soon as possible, and then after these are done sit down one weekend and just do readings. For example, this weekend dedicate yourself completely to your assignments. Next weekend, make it readings. Just don't leave anything until the last minute because that will not help. Also consider reading a chapter of a textbook or readings etc. before you go to sleep each night or when you wake up in the morning. (Hopefully you don't sleep at 3am, sleep is important to helping you relax and get through the day!) Then you will not be falling behind and revising for your final exams.
If your still feeling overwhelmed once you've organised yourself, then you need to consider how you can improve next semester. There is no point on looking back on what you did wrong if you don't make a concious effort to improve.
1)Speak with a co-ordinator at university to find out what options are available to help you manage your time better.
2)Consider doing less subjects next semester. Some people do find 4 too many. 3 subjects will still make you a full time student so you can get concession fares etc, but you don't have to be at uni as much and won't have as much to study. You can also become a part time student (1/2 subjects). Don't forget that most unis offer classes in the holidays. These are shorter than a normal semester, but count equally towards you degree. It's a great way to catch up and not make your degree seem like its taking forever.
3) If you have a job, consider leaving if your education is more important. Many of us don't NEED to work while at uni, so if you are maybe consider if its necessary. If your parents aren't willing to support you, Youth Allowance could be an option for you to get by.
Uni shouldn't be an overwhelming experience. If you can keep on top of your work it will become a much nicer place to be