Lack of Opportunity at work - Am I being discriminated against?

I'm reaching out for advice regarding a challenging situation at work. I've been with the company for nearly two years (as of October 17th) in a fairly independent role overseeing marketing data for our global recruitment business. I am fairly gifted with numbers, so its been great! 

Shortly after joining, my manager left, and I unofficially assumed departmental responsibilities. Over the past 18 months, three job opportunities within our department have arisen. Despite my interest and unofficial performance of these roles, I've been either ignored or told I couldn't apply. These positions offered salaries 10-25k higher than my current compensation.

Recently, a new 'Global Head' from a competitor joined our department. While I understand my experience is primarily EMEA-based, not APAC, a new position has since been advertised with a job description 95% similar to mine, offering 25k more than my current salary.

Prior to the new Global Head's arrival, I proposed several ideas and practices to improve efficiency and reduce costs. These suggestions, including one that saved the company over 600k last year, were largely ignored or dismissed. However, the new Global Head has implemented many of these same ideas, including bringing in a new supplier I had tried to for a long time..

Despite my contributions, I haven't received a pay rise in two years due to supposed budget constraints. Yet, the company continues to advertise roles similar to mine at significantly higher salaries.

Because of my autism, I find these conversations challenging. I'm passionate about my work and have dedicated myself to this role, but I feel my progress is stagnating while new hires are brought in around me.

Has anyone else experienced a similar situation? I'd greatly appreciate any advice or insights you could offer.

Thank you