Very insecure and fearful in relationship

I am dating a very attractive and charming guy, and I have a fear of being left when he meets someone 'better'. We have been together for almost 11 months, and while he is a very loving boyfriend, I am insecure about whether I am enough.
He always has girls interested in him, just before we were dating there were at least 4, and since we have been together there were one or two.
On the other hand, I very rarely receive any kind of attention, I had a creepy perv who went around every single girl in my friendship group coming onto me after everyone else said no, and 50 year-old men in vans, but that's all.
Before we were together, he liked the same girl for years. They never dated, but he said he always felt something for her. They were good friends but they don't really speak these days, though they were close for the first few months of our relationship, but apparently she liked him too recently. That made me feel as if I had stopped them being together or something, since he wanted her for so long.
He told me about a certain 'look' he likes on a girl, and told me how hot it was. I don't really fit the description, and it makes me insecure that he will meet someone like that and be more attracted to her, despite him telling me I am beautiful and such.
He has said in the past he wouldn't leave me, and he has said it would be quite hard to find someone better than me, and he isn't exactly looking, but still..
I am always trying my best to look good for him, to try and be interesting and funny and impress him. I am just sick of feeling like this, and dreading the day when he breaks up with me. Please could anyone offer any advice to stop feeling this way? I would be really grateful, thanks in advance.

He's been with you for 11 months, that's got to count for something Even if you don't think you match his description of what he finds hot, there must be something about you, say your personality, which he may find more important and adores you for it

Hi there,
I totally understand what you mean. I had a similar problem myself some time ago and I know it can be hard for you!
But don't worry so much! Look, he really does like you. Otherwise he wouldn't be with you for so long. You've been together for 11 months and that's a pretty long time.
It's normal you try to look good for him and it also shows that you care a lot, but never change the way you are for him! He's interested in YOU and not someone else.
Don't be afraid he'll break up with you, because this thought can only hold you back and make you lose the best moments of your current relationship!

Last piece of advice, don't try too hard because he'll notice you're acting weird. If this situation still bothers you, try to talk to him and be open about your feelings and fears. Let him assure you everything is fine and maybe when he realises you're feeling insecure he'll change! :-)

You just have to trust he likes you to be honest. Have a talk with him, seriously, and tell him how you feel insecure and how you feel he'll wonder off with another girl. Total honesty is always the best way forward in a relationship.

Thanks for the advice We did talk about this in the past and that made me feel better, so I do not know what it is that made me feel this way.
The girl he liked for a long time said one or two things which were not nice about me, and was saying stuff like she was thinking about him, texting him during the early hours, etc. so it seemed obvious she liked him. I never met her, but I found it difficult to know he liked her for years, there must have been so much about her. I found myself analysing the way he spoke to her on facebook etc. (from what I could see) and deciding if it was flirty or not. But, he said they have drifted apart/she ignored him etc., so now they are not really friends.
He is friends with other girls (even one he dated a while ago) and I really have never felt the slightest bit jealous or had any problem.
I feel like an idiot, I am scared to push him away, I just need to know that these other girls do not possess lots of qualities which I do not. I just need to try more... thanks for the help x

I suggest, in ignorance to a relationship, personally, that you set some boundaries, and say that they will help you recover and better your mental state. I'm not suggesting that you are by a large degree mentally unstable, but if it helps maybe telling him to cut down on texting to girls that have a crush on him, or make him say to them he's not interested in being anything more than friends.

Yeah, I feel like I do not have a right to . I honestly would never have any problem with him chatting with girls and meeting up, I think to tell him to not would be very possessive and controlling.
The girls knew he was with me, but sadly I have encountered people in my life who do not respect the fact that someone is in a relationship.
He is a very friendly and charming guy by nature, and it sounds silly but sometimes I wish he would feel jealous about something, just to stop me feeling like a freak. But, I would never do anything to try and make him jealous, I do not agree with that.