How can I make my parents understand my distress?

It isn't easy to try and make your parents understand your distress, but if your parents really love you, they will try their best to understand you. Explain your problems with them and let them do the rest. Make sure you tell them in a state where their full attention is on you.

Talk to them about it. Tell them or show them how you honestly feel. If you write, then maybe write all about it and then show it to them. If you draw, do the same. They will probably understand.

Generally speaking, clear and thorough communication is the best way to help parents understand what you are going through. Talking about how something is affecting you and how it makes you feel can help them understand how to react and best help you in whatever you are going through. No parent is perfect and not everyone can understand exactly what another person feels but they can try and the very face that you are putting yourself out there and being honest about how you feel is enough incentive for them to support you. A lot of times, trying to explain why you feel something can also better help someone else get where you are coming from.