hello Dana, it's great you are looking after your friend, although you are stuck and what's worse is that it's affecting you now.
Firstly you need to look after yourself, because if you aren't strong enough, or aren't to cope with your friend then you won't be able to help her.
You can only learn so many coping mechanisms for each situation and when you had anxiety before, now it could be a totally different situation, so you may not know how to cope with your friend suffering from OCD and depression.
Remember when you had anxiety before then depression would have been right behind you and add onto your anxiety, simply because they are both joined together, however OCD is caused by anxiety and I've had it for many years and know what it does to you.
You've been looking after her for 3 years and it probably seems as though it's only going around in circles, so tell your friend that you have booked an appointment with a doctor and you will go with her, and tell her that there is help out there but it won't come to her she has to try and seek out help from those who are experienced, but you will be right behind her.
By saying this she could go with you to your doctor's appointment, she has to start somewhere. Geoff.