I feel for you because I felt equally as rubbish when I first came up here. I'm from Chichester (no idea if you've heard of it, it's about twenty minutes away from Portsmouth) and made the decision to go to Glasgow University, even though I'd applied to and been accepted by some reputable universities which were closer to me, like Sussex. In the first few weeks/months up here I went through some teething problems. I couldn't adapt at all, missed home and my family, and struggled with confidence issues so felt like nobody liked me or wanted to know me. I also wasn't spending time with the right people, so felt utterly bored and awkward when I did socialise, and subsequently felt even more miserable.
It basically all changed one Friday. I got back from university, did some washing, and literally bumped into someone I'd met right at the very start of freshers week and arranged to watch a film with him. This introduced me to his group of friends, who were starting to merge with the girls I knew. Finally I felt I was with a group of friends who liked and wanted to be around me, and who I liked and wanted to be around too. Two of my best friends here are from that group, and I spend ridiculous amounts of time with each of them, either talking/watching tv/laughing at various ***** in and around our halls/going out to the pub with and so on. We may not be the same age, from the same place or have exactly the same interests and tastes but we all get on very well and have a good time and I feel lucky to have met them all.
You need to bite the bullet and, in regards to the friends you've made off your course, invite them out somewhere! Yesterday I went to the pub with a friend I've made here because he wanted to watch the football. I have no interest in football and it was Rangers vs. Celtic beforehand so I knew the pub would be a bit of a nightmare, but I went anyway. People aren't going to want to be antisocial and won't think you've imposed, they'll probably be glad you've asked them to do something.
good luck; let us know how it goes x