Hello User, a very good question you have asked because for someone with this disorder, how can you explain why you have to check the door locks so many times, a number you have created for a certain reason, my number is 4, although I may still do things more than 4 times, it's just that I need to count to 4, then I'm satisfied.
At my age, I have been able to hide my obsessions and compulsions so nobody knows, but it may take a while for this to happen to you, please don't worry, it may slowly happen, depending on any grief other people give you.
Your parents might already know that you are doing things and don't know why, but remember you could first talk with your grandma who has already noticed, that all depends on you, but you can write down what you have done or currently doing, which they may relate to, and mention you have been on the Beyond Blue website and spoken to people who can definitely recognise what you have been saying.
Tell them as much as you like, you can go slowly telling them or go the full hog, tell them you have these feelings which are telling you not to go to school because (give them the reason).
It's doesn't matter what they say, such as it's not going to happen, because for you it is and it's a disorder you need to speak to your doctor about and if you mention 'the mental health plan' this will entitle you to 10 Medicare paid sessions, so no cost for your parents.
If you are 25 years or under, you can contact Kids Helpline 1800 55 1800 by phone, webchat or online and will assign someone who can relate to your age, but please don't forget us.
Remember if you do have OCD people will have noticed and may have said 'it's because you are under pressure at school or you might have an exam to do', ok yes that may be true but after the exam, you still have these thoughts, obsessions etc, but please don't worry we want to help you as much as we can.