You do not need more time, you need to get help. Your friend sees it and I think you see it too. For whatever reason you are afraid to seek it but, if it is depression, its a very hard road to travel alone, and the battle may become too much. Your friend wants to see you happy and whole and that's why they are forcing the issue, they can see your struggle.
So tell your parents. Seek their support for the fight ahead. Get to your GP too. The more you have on your side the easier it is to win the fight against depression.
Do this NOW, not later, especially if you are self harming or indulging in risky behaviours like using drugs or alcohol to self medicate. Immediately if there are thoughts of, or talk of suicide.
Your friend is doing this because they care, they see in you something worth fighting for. Take up that fight too. Seek the help you need. Recognise there ARE people who care and love you enough to stand by your side throughout this .
The road ahead may be hard and long but you are far from alone on your journey though it. Good Luck!