Hello Jay, and a warm welcome to the forums.
Enrolling in uni is a great achievement but if you're suffering from anxiety and depression then perhaps the thought that uni may be able to overcome this feeling may or may not suffice, but this depends on many different circumstances that could affect how you want it to be and may differ from day to day, your social life as well as the demand to fulfil all the requirements by the due date.
Overthinking can create negative thoughts if you're suffering from any mental disorder and it's never easy to try and push these away, simply because they only seem to dominate how we feel and extrapolate into the next day.
What you've said is not rambling, it's only opening up to those who understand your predicament and want to help you.
There could be many different situations that happen but caused by triggers you were unaware of, these need to be identified by someone else, and probably a uni counsellor, doctor or a psychologist so they can discuss different alternatives so you will be able to cope.
Can I ask what your intentions after you've finished this course, but please remember you can only go at your own pace but would like to hear back from you.