Is it normal to live in the present and fantasy worlds most of the time?

I'm a 20 year old girl and I know people my age who are working towards serious ambitions they want to acheieve. But my ambitions seem fantastical and I've never been able to choose any realistic career so I've settled for high-school English Teacher. I just can't see it happening realistically. What I want to do is be a professional musician. And better yet,a famous musician! I know as well as you that that's VERY unlikely to happen. Yet, THAT's my ambition.

I'm in my first year at university, studying Literature. I enjoy my degree but I still feel quite unhappy. Although I complete assignments and mostly get B's, I've began skipping most lectures and have missed a few seminars. I get angry at myself for this because going to university used to be one of those unattainable goals for me.
I remember my mum would often let me 'stay off' school. I was late whenever I did go. Skiving continued through to high-school then into jobs(though the late problem eased a bit). I hated every job I've had but uni is enjoyable.
Now I know a lot of people hate their jobs but I really hated all of mine - dreaded every day and felt really bored and depressed, counting every minute until my day or shift was over. And then I'd either get fired or leave.
So upon reflecting on THAT, I could see that my social anxiety might be part of the problem there. Even as a young kid, I had low self-esteem and although that's improved some, my anxiety seems to have gotten worse. I always feel unnatural when talking to anyone who isn't a close friend or family,even talking to people I see at uni everyday makes me timid, embarrassed and AWKWARD. I haven't really had panic attacks except for in seminars whilst I'm talking and people can tell I'm nervous and slightly out of breath which is humiliating.
But I'm a different person round friends and family - talkative, often laughing and being funny/witty, and I think I come across as quite intelligent. So I feel like nobody else knows anything about my personality because it disappears. I think I come across as quiet, maybe quite nice but a little dim and a little weird.

So the pattern so far predicts that I will either leave or be kicked out of uni. I really don't want this to happen because it's my gateway to a better life and I enjoy it. I know I have free-will and I can choose but sometimes I feel helpless to the rut I'm in. It's like I sum up this courage to do something really irresponsible and I kind of can't believe I've done it - things like just deciding, 'Fuck it, I'm never going back to that stinking job!' I'm in a world of my own!
I told my dad about all this and he shouted at me that he works five days a week, and he's worked that plus more ever since he was 16, now and he's 53, because he had a family to support; he had no time for the pub and friends, etc and I should be thinking myself lucky and take every opportunity I get, and I KNOW all this, and I even AGREE - I don't want to be a fuck-up!