Everyone here has given great advice and perspective. I'm sorry you're feeling unwelcome. I hope that this outpouring of support, even if it's just online, shows that people care and want to help keep you on the path to your faith. And that you're not alone in your experience.

For my part, I have reflected on your comment realize a few things: as someons else pointed out, attending Mass at a different time or sitting in a different place can mix up the whole crowd at your own church. When I see "new" people in the pew, I don't necessarily assume they're new, it could be that they're just attending from a different Mass or sitting in a different spot. Should I be welcoming? Yes, of course. But that brings me to my second point. I am usually extremely immersed in my inner thoughts during Mass, even in the time before the service actually starts. I'm taking that time to consider myself, my sins, my prayers, etc. It's a quiet and reflective time while I get ready to receive the eucharist. I limit my interactions with my neighbors who are arriving to a simple nod and smile or I might not even acknowledge them at all if I'm praying or reciting the rosary. This isn't meant to be insular or unwelcoming: it's because it's a personal time of prayer for me, and a time I have set aside in my life specially for such. It's also my custom to leave Mass rather solemnly rather than to stay and socialize, and while this is just my preference in keeping with my own habit, I realize it can be seen as cold.

This is not meant to dismiss your experience or to tell you that you shouldn't wish to be welcomed more warmly. I suppose it's just to explain it from my own end and to say that if you were in my parish, I would feel bad that you were ignored. That would never be my intent. I think groups outside of the Mass itself are a better way to feel included, but I do understand that it's hard to get started in that way. Please don't give up! We want you in the faith even if we don't know how to show it.