I what a boyfriend but no one seems to like me, I'm 17 almost 18 and have never been in a relationship, I'm not ugly but not gourgeous I'm pretty standed really. I have a grate personality and a good sense of humour, I think the only thing that might put guys off is my weight I'm not fat-fat but I do have a bit of weight on me, I'm size uk 14-16 but surely that can't be the reason why I'm single. I take good care of myself and dress nice.

Is there anyone who can tell me what I'm doing that's not right? Is there something I can do? Does weight matter?

The best way to find out is to have regular friends. They get you out and about, they tell you what they think without being too delicate or too mean, they introduce you to guys, they are there to have fun with while you wait to find someone, they are there when breakups happen, they are 'friends to the very end.' If you don't have friends, that would be what I would wonder about first.
Weight matters to some but not to others. Same with height, hair, and all sorts of other things. If you are nice to people, ask them about themselves before trying to impress about yourself, have interests you can share (books, sports, games, cooking, photography. Doesn't matter) you will find that you have friends.

Just keep getting to know more people. You can force someone to have feelings for you. But by knowing more people, you increase your chances of meeting someone who's compatible with you and possibly have feelings for you too.

I like your confidence. That's a really positive trait and you should hold on to that. Aside from that, no matter what you look like (to a certain extent), you can't just wait around for people to approach you. A personal story of mine might help you get some perspective. I would also consider myself pretty good looking and in shape, and I also did in high school when I was about 15-18. Somewhere along the line, I got the idea that I could just wait around for girls to approach me. Well, that got me one girlfriend in four years, which lasted about a week.
Anyway, senior year I was actually reading Dorian Grey, which somehow got me hyped up to sort of take my life into my hands. I thought of the girls I was interested in, I came up with four girls from several of my classes. I spent about a week actively trying to initiate a conversation with any of them, as much as my shyness would let me. Finally, I asked a girl about the homework as class was ending and we wound up walking to our cars together. That became a routine, and I've been dating her for four years now.
The moral of the story, I guess you could say, is that if I had kept sitting around waiting, I wouldn't have met my girlfriend. All it took was effort on my part and it suddenly became a lot easier.

Good luck!

I think that even really knowing what a relationship is begins about 17 for most.
That is still just the start of the learning process.

Because a boy and girl go out , and hang around each other at 14 15 or 16 is not really a relationship.

Your time will come, be patient.
Your post is thought out and well composed.
The grammar and spelling is correct which shows
You are intelligent and thoughtful.

The other people here have given you
Some very good advice.
You should give some of the ideas a try.

Remember this also,
Sometimes quality takes longer to recognize.
But someone will soon.
I'd bet on it.