Hi,
I'm sorry to hear about this and understand the stress it can cause on your Student life. Confidence was a huge thing for me too at University and something I struggled with a lot when approaching people but I managed to look at situations in a different way and that helped a lot.
I'm happy to hear that your flatmates are nice compared to your previous experience and can understand that they are studying and working the amount that they do (depending on if you mean working as in studying or a job), however you could use this scenario and look at it a different way, maybe suggest a study session with them, where you all study together even if you are on different courses, learn more about each others studies and this can not only benefit their studies when explaining it out loud to others who may not fully understand that course like they do but also gives a topic of conversation to start building those friendships and understanding among you.
Also you mentioned that there can be financial issues among your flatmates but there are plenty of other approaches to this that are cost free, maybe you guys can just hang out on your campus and see what it has to offer, my university's student union has loads of events to take part in from quiz to karaoke nights, pool tables and so on or look at cost free ways in your area and see what that has to offer and I'm sure there's even more to do just within your flat like games or even your own quiz nights!
Shyness, from my own experiences, can become really frustrating to get past and can feel like you're kicking yourself after missing the opportunity to talk someone due to it, a way to overcome this is to understand you're not alone in this at all and it's understandable that you feel the way you do. Again student union events can be beneficial for this as they encourage interaction between students, even if you go to these alone, there is nothing wrong with that and can be a good push for you in your confidence among other students who may feel the same as you and need that push as well.
I hope this helps and good luck!
Katie (Film graduate)
University of Wolverhampton