Lonely and left out - what can I do?

I live with my two friends in uni halls. We are planning to live together next year, and have sorted out our house, but lately I have been feeling really left out with them. They are always in each other's rooms and don't really ask if I want to join in, and I'm started to get really paranoid. I have to be out a lot as I have a job, so I understand that they are likely to be a bit closer because I am not always there. I'm just wondering if anyone has any ideas about what I could do, because this is making me feeling really hurt and I'm obsessing over it really badly. How should I act, and is it worth speaking to them about it?