Is this just my imagination or am I really like this?

Oh I am the exact same! I am 20 nearly going to be 21 next month- but yes I am totally like you, I sit at home and hardly ever go out. Just have a couple of friends that I see once in a blue moon for a couple of hours but thats it. My other friends have kind of grown apart because I used to go out but not anymore so I feel like I have lost out on loads of friends but since I am extremely shy I always felt awkward while out with them so I just stopped going. SO now I am just the same as you, but I know one day it'll get better, It always does! So keep optimistic and for the time being just enjoy being lazy and not having to do anything! :-)