Do i have autism? i do a lot of masking, stimming, and have very bad social anxiety. how do i bring up this topic? and is there a reason to be concerned?

It does not sound like autism tho it has many variants. Pl see a good MD and explain your problem to him/her and you will be treated and be fine. Don't worry

First please have a complete physical exam by Doctor to know if you have an illness. Please see a Clinical Psychologist with expertise in multiple types of psychotherapy for a diagnostic evaluation and for help. This will help you to know if you need medication from a Psychiatrist.