I don't know much about autism but I can say from my own experiences with doctors that a doctor telling you you are not diagnosed with something does not mean you aren't, it just means this specific doctor thinks you aren't. Doctors are too often trained to never trust you and dismiss whatever you might be saying.

I still think you should try and get an evaluation from a doctor if you think you might be autistic, because getting an actual diagnosis is helpful, but if the doctor says you're not, that shouldn't stop you from learning about autism, trying stuff out and seeing what sticks. No matter whether you actually are autistic or not, if living like you are autistic helps, then do that.

self-diagnosis and self-evaluation are valid, but be careful about it. you could massively improve your mental health, or ruin it. so do your research and don't take extreme measures.

whether you want an official diagnosis is up to you; all it really does is give you something you can show to prove you need accomodation. it also has the downside of potentially denying you rights on the basis of your disability or leading to abusive treatment regimes. it depends on your circumstances whether the positive or negative side shows more, for me it's about neutral.

what's really important is that you accept yourself regardless of diagnosis and don't spend your life trying to conform to social norms that are slowly killing you.