what do I do now?

Hi I feel like I really just need to vent and let out my emotion so I hope you don’t mind if u do so here and maybe receive a little advice along the way? Recently I have been very distant with my emotions and keeping them under control. Last year I think I went through a state of depression (or sadness you could say as I was undiagnosed) for a while as of the fact I had little friends and not much of a social life in school and out school. After 6 or so months I had finally managed to fall out of this awful state (in the summer) and had found a new friend group and everything was going perfectly and I was the happiest I had been in years. However recently going back to school I have discovered my new “friend” group actually hung out without me a lot leaving me uninvited and they talked about me regularly. Finding this out was a very big upset to my life, almost as if they had just made my life and then threw it all back in my face, leaving me almost empty and almost friendless. This happened a few weeks ago now but I fear my life has took a turn for the worst and the old anxious, always chocking back tears, emotionally unstable me is slowly returning and taking over my life, I value relationships in my life a lot but I have been left with only a few friends who really aren’t that close to me or interested in me and are invested in their own lives, apart from one who I spend most of my time with but it just doesn’t feel right. I just feel as if my world has been shattered and I have nothing to look forward to these days, just continuous school and watching my old best friends slowly forget about me. Obviously I don’t want to return to my friendship with them because they have made it very obvious to me how they feel about me but I am now left feeling empty and nobody wants to be my friend because I’m not interesting or fun like others. I was wonder if I should go to the doctors to talk about my poor mental health but I don’t really want to talk about my sadness with my parents because they a lot of the time just think I’m being over dramatic and don’t understand. How could I lead a happy life living with few friends? How can I distract myself from this? Do you have any other advice that can stop this from taking over my whole life on top of my school work? should I see the doctor for a mental health check? Thanks for reading