Self doubt holding me back - low functioning autism

Hello I'm Glitters and I'm autistic and also have ADHD.

Since I was little I've loved animals and have always been excited at the idea of working with animals as a veterinary surgeon. I'm lucky enough to live on the outskirts of a town in the country, there's a lot of space and a good sized building that's used for storage. If I become a vet I could use the building as my practice where I could treat the animals.....

But! 

I'm low functioning and as people constantly tell me I'm stupid I don't know if I'm even capable of being a veterinary surgeon and that is really upsetting for me. It's my passion and my special interest! I don't want to do anything else. I constantly research animals, watch videos on animal health and welfare, read books, lookup equipment...

But it all feels like it's for nothing. I don't know if I'm smart enough to get through training. No one believes in me and I'm nearly 30 and I worry that there's not enough time left for me to do this.

I feel like I want to just go for it but my anxiety is so bad I feel like I'll just spend the rest of my life dreaming and wanting but never succeeding.

Do you think it's something I should pursue?

Does my lack of intelligence mean I'll not be good enough?

I don't know what to do.