i know exactly how you feel, some people think conversation comes naturally to everyone but it can be really hard. i used to find it really hard to strike up a conversation, and still do sometimes, but i have decided that whoever said confidence is largely about faking it is completely right. you just have to smile alot and look at who you are talking to. and as another poster said, ask questions, it makes you look really interested and it takes the pressure off you. one of my friends told me about an elastic band trick, and now i do it all the time. i get really nervous speaking to people and used to fiddle with my face or my hair, and when i realised i was doing it i would feel even more self concious, so now i always have a hairband around my wrist and if i find myself starting to fidget i start to play about with it with my fingers, it is less obvious to others and it helps me focus on "confidence".
about the guy you like, well either you can bite the bullet and tell him, or wait to see if he tells you. if you cant face it maybe write him an email saying "I really like you, if you like me to tell me if not can we just pretend this email didnt happen?". i would find this easier to handle than telliing someone straight i fancied them, i have no guts to do that. it sounds like you are good friends anyway so you have a good base. or maybe you can get another friend to find out in a subtle way if he is interested for sure, and then it might take away some of the fear of baring your soul?
and you probably will open up at uni. you are living with new people, seeing them every day and will probably just want to die at first but after a while you will get more comfortable with them, and afterwards you will feel more confident about meeting new people in general. you may well still be quite shy but you will have the confidence to talk to people and enjoy the company of new (and old) faces rather than fear them cause you have nothing to say. its hard but trust me! a confidence course might be good but if you dont think you could face it maybe buy a book? i started cutting out articles about confidence from magazines like cosmo and putting them in a folder (cause i am a geek), and they are a bit cheesy but sometimes have quite good tips.