I would suggest talking to your doctor. They will probably refer you to a specialist who will be able to diagnose you.

I can help you. My son is autistic. I can usually tell if someone has autism by looking at the move or talking to them. It's much easier to see in males. What is your age and gender? And what makes you think that you are possibly on the spectrum?

Okay so self diagnosis may be controversial (especially recently and even more so when it comes to Autism) but the biggest help in my journey was taking and understanding the assessments before I went to any professional. The two most common ones are the Autism spectrum quotient and the Camouflaging Autistic traits questionnaire. There is also the Ritvo Autism and Aspergers diagnosis scale and a specialized test for girls/women that are more likely to mask and not show obvious traits. After that there are several options to seek out official diagnosis through a GP, therapist, or various specialists.