What you are feeling right now is quite normal and lots of other people will have reached this 'a bit glum' feeling at this point. After all the excitement of Freshers Week and 'I'm at University!', that initial feeling of euphoria has disappeared and you feel a bit ... lonely and deflated.
Its a good idea to see a counsellor as suggested above - this really will help as they are very used to dealing with homesickness (because that is all this is, promise) and they will know how to help you get back on track.
In the meantime, try not to sit in your room all day. Even if you don't feel like 'going out' with friends, make sure you do things like going for a walk every day and get to know Bristol a bit. There are heaps of interesting bits to explore - the Harbour, the Suspension Bridge, little shops in Clifton etc. This way you will start to focus more on 'what I like here' rather than just 'I miss my family'.
Write yourself sticky notes about something good/fun/interesting that happens each day and stick these all over your wall. Re-read these a lot, and you will see things getting more positive and that you feel more optimistic.
Hang on in there - it does get better, promise.