You dislike them because they are constantly belittling you and don't respect your boundaries.

Going to a psychiatrist could be very helpful because they can prescribe things that can help the anxiety. A therapist could help you manage and cope with triggers. They can also help you work on your self confidence. If its possible you should move to your grandparents.

If anything, take your parents offer and see a shrink. Tell them you want to make an appointment and go. The worst that could happen is your parents complain but then you can tell them that they offered.