I'm surrounded by people, yet feel so alone, what should I do?

So for context in the past two months I've split with my partner of 2 and a half years (I wanted to fix things, they didn't, so we parted ways - it broke my heart), started university - still regrettably living at home but the costs are too high for now - and have spoken and met lots of people to try and make some friends. I still speak to my one remaining friend from college who has gone to a different university and we talk often.

I spend most days surrounded by people, in lectures, at work and when socialising. I laugh and joke with them and generally have a good time in the moment, but despite all this, I feel so lonely, just empty. I feel that whenever I speak to any of them I am just annoying them, that they'd rather be doing anything else and are simply accounting for me just because they feel they have to, that I'm just an inconvenience more than anything. I try to make an effort to arrange to see eachother and to make plans, but they've all got other friends, and I just don't - so usually nothing comes of them yet they do things with their prior friends and even tell me about them, yet don't ever invite me along.

So, reddit, what if anything should I do - how do I shake this feeling?