I dnot know ...

High school can be tough and 17 can be a difficult age. Some girls and guys of your age can be very shallow and critical at times. I'm sure you're well aware of this. Blending in isn't always easy.
Certain behaviour and actions make people leery. You say people really like you at first but pull back later. Seeming over-eager or clingy can do this. Don't be too intense, try too hard or touch too much.
Most people love to talk about themselves and love compliments. Focus on them if you're truly interested and give one sincere compliment in an off-handed way. Don't go on and on about yourself trying to make a good impression. You'll come as as self absorbed.
People like being around others who are good natured and positive. Nobody likes complainers, gossips and gloomy or nasty people. Don't let your bad side be your only side.
You may already have these few points in check. There may not be any problem with you at all. Sometimes only time can straighten out this kind of stuff. It's part of being a teenager and growing up. We've all been there.

Tried Breaf Mints? girls like good breff.
ANYWAY...
I'm really weird and I have your same problem. BUT when you find people to hang with you will know they are not shallow. You sound like a normal non-shallow person. Just relax and remember "quality not quantity".

hey don't worry about it, you're at an awkward age. i didn't have a boyfriend till I was 17. suddenly around the time i was 19 i was having no problems finding dates. for guys at your age physically and for many girls, the best is yet to come. a lot of guys start to fill out everywhere after high school and everything comes together.
now as for people avoiding you later, from my own experience that is probably just teenage oversensitivity and looking too much into people's actions and thinking that you make that much of a difference to the way people act...that's normal for a teenager. next time you start thinking people are trying to avoid you, take into account the hormones and then consider the fact that sometimes people are less friendly not because of you, but because they're having a bad day, or were just in the middle of a deep thought or something.

Well, thak you for advice ,i am perhaps a litle over aged (when i talk to someone from a chatroom, they ussualy think that i'm around 26 ... and than they say that that is a good think ,and situation abviosly says something opossite ...

just a regular everyday stud muffin ain't you

That happens to me all the time. Sometimes when i first meet someone they seem to really like me. Well i do have good looks, im polite, pretty damn funny sometimes and smart but then they seem to want to avoid me or ignore me later on. So im like what the fuk? fine. THis doesnt happen with everyone i meet. oh and im not over - eager or that crap either. oh and im 15

This pesky user has been removed for repeatedly abusing other users and being a pain in the butt. Behave or you will suffer the same fate. - The Management

I know how that feels. I was 22 before i had a gf. I realised that there was something i was doing wrong with the conversations i was having. I'm still not sure what it it. i think that basicly i became annoying to people i wanted to befriend. I needed to take things much slower. if someone gave me a phone number, i would call them just because i could (hey they're my friend now, right?) but they didn't want to talk about nothing like i did. i'd call again the next day. now they were annoyed and sorry they gave me their number. I've realized i need to relax. If i think about what if's then something goes wrong. just take things as they come, and let things happen. it might not hurt to periodically think back about conversations you had with someone where you thought you made a fried but soon after nothing came of it. but in the end you must alway look forward.

You might just have a problem telling when someone likes you. If you have the slightest hunch a girl likes you, ask them out, or at least stop and make some eye contact and small talk. They'll appreciate that you took the time to talk to them, and their affection will likely become more obvious after that.