I've always grown up with a feeling that i'm perceived and perceiving different to others. i'm scared to open up for fear of how i am thought of. could i be autistic or do i have a different mh issue, or is it normal?

You need to find a life coach/therapist that can teach you some relaxing and stress reduction techniques. During the process you may also explore your mindset. I don't feel autism is realistic idea, but your confusion & lack of confidence/self-worth is a fixable mental health issue.

Recommend you seek psychiatric or psychological consultation to achieve a proper diagnosis that will allow specific targeted therapy. Have found that cognitive-behavioral approaches can often achieve great success in brief periods of time.

It is not feasible to provide an opinion without additional history, physical examination may be some tests. It would be prudent to see your doctor to see if you may be depressed. Depression is treatable. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!