Hey! I'm sorry to hear you're struggling, but please know you're not alone in feeling this way and it's brave of you to reach out on here and speak openly about how you're feeling.
I'd say to just take it day by day, small steps lead to big wins. Something small you could try doing if you're comfortable is to ask someone in your class about a lecture topic, or what their working on etc. For me, I find it easier to speak to someone when it's about something I love, such as TV shows, I can go on and on about my love for shows, so if you're able to find a common ground with someone hopefully that'll make conversation that bit easier.
Maybe you could try follow a few coursemates on social media, and reply to one of their stories to initiate conversation. Maybe they've shared a photo of a meal or a nice coffee, you could ask something like 'that looks lovely, where's this?'. Does your uni centre have any social media groups for students to get to know course mates? Complimenting someone can also be a good way to start conversation, whether it's their style, or just their notebook they've brought along with them to a lecture.
Do any of your fellow course mates study together? Or could you try come up with the idea to create a study group? If this evolved into regular meet ups you could then suggest all grabbing a coffee together afterwards. Another idea would be to keep an eye on any events happening at your university centre, is there any upcoming seminars or workshops? Just being around people with similar interests can help, seen as you've said there are no clubs or societies to join.
I'm sorry to hear you're college and high school friends are not being friendly anymore, is there any of them you could consider reaching out to, asking how they are, that you miss them, and ask if they do want to go for a walk or grab a coffee?
Just remember you're in a new environment, it's a big change, and of course you'll be feeling all these different kinds of emotions! It's incredible that you're reaching out and acknowledging you want to change how you're feeling, so you're on the right path for sure. Things take time, so don't give up hope, I'm sure you'll form some great connections with people soon. When you're feeling lonely please keep in touch with your loved ones, and consider speaking to a counsellor or the support services at your uni centre who can help you get through these challenges.
Best of luck! ❤️