Scared of penetration

I’m an 18 year old girl and for some reason I’m terrified of penetrating my vagina with literally anything. I’ve tried multiple times to insert my fingers, a toy and other items but I chicken out and get literally filled with anxiety. The thought of someone else penetrating me doesn’t really bother me but every time I try for myself i just can’t and it’s mostly mental I think but then again I haven’t gotten far enough to know if it’s physical as well.

I know it sounds stupid but I just want to prep myself because I want to lose my virginity and I don’t want to be caught off guard and I want to be prepared but I just can’t

Any advice?