Welcome to PC. You can find a ton of support and understanding here. We are there and have been there.

People find it tricky telling their parents because sometimes parents can be in denial or can just be very unsupportive. I wouldn't not tell them for the sole reason that you think it would be a burden. You need help and they might be in the best position to get you that help. If your parents are loving, caring, supportive people I would encourage you to tell them. Families that are fairly healthy will share each others burdens and help each other.

Are you in school? is there a school counselor you can talk to?

At 18 you are an adult and can seek treatment on your own. Sometimes people here will research for you what resources for free or low cost may be available in your area. If you PM me where you live I am happy to do that.

I don't think any of us can do this alone. We need lots of support. I think you should seek professional help but there are things you can do on your own. I dunno about schitz but anxiety and depression can be helped by CBT, mindfullness, meditation, journaling, DBT, diet, exercise and so on. You can teach yourself CBT and practice its techniques. There are lots of resources on this site.

Start here-
In-Depth: Cognitive Behavioral Therapy | Psych Central