Is it normal my life feels so far away?

Hello.
I'm a shy girl, and I've never had many friends, I don't enjoy going out clubbing, I have a couple of close friends(not a group) and I see them a few times, at least once every 2 weeks, I go to the gym and I go to a art class, I'm trying hard to meet new people and make friends. I've always been kinda 'I'd rather stay in' no one invites me out much and if we do go out it's to the cinema, or bowling or for a meal and a couple of drinks. I've never had a boyfriend but I've been interested in 3 guys.. Maybe more ;) but I've never had the confidence I thought things just clicked and that you didn't have to look.

Recently my sister got a boyfriend and she's out every night with him, all day when she's off work, and my mum is pestering me to go out more, she says she worries about me and she wants me to go out and have fun, but I'm happy... My sisters boyfriend s brother asked me out so I went on one date and knew I wasn't interested but still my mum pushed and still is doing, i go out as mates with him a few times just to keep my mum happy, but she says things like I'll end up on my own or with no one, it just hurts makes me feel like a failure and I break down and cry. Cause I've never had anyone and right now I don't want anyone, but will that stop me being with anyone in the future? Is she right? She knows I don't like the guy and she's pushing. Btw I'm 21 and it just feels like if I don't do what she says my life will be a mess :(

I want a husband and kids one day... But I'm happy :(