I did read your other posts about exam worry (did you pass after all?) and your sister's situation. You have been having a tough time and anxiety is something that realy does need to be addressed, so I'm very glad you have decided to do something about it. Getting the right help was exactly what I needed, and I'm only sorry I left it for so long.
One good thing is you do not need your parent's knowledge or help to get assessed and treated. Even so it can be a pretty daunting thing to try to do. I found not only was it very hard to disclose what has been happening but trying to do so face to face seemed just too hard. I worried I'd muck it up, or forget things, or even chicken out.
Can I suggest you either see the uni student counseling service or a GP and have a long appointment? There hand over a paper which you wrote well beforehand. I used point form and took a couple of days, so I'd have time to make alterations and add things until I had an accurate and complete account of what had been happening to me. I've done it more than once and it's been good, the doctors appreciated it too.
From then on it was easier as I just had to answer questions and clarify what I'd written.
You can take things a step at a time, getting medical help being the essential first action, then deciding what to say to your family later on.
Does all this sound possible?