I have had the same problem, I'm 6'3" and weigh just over 10 st, whatever that is in lbs.... I never felt cool or attractive, things made me look stoopid.
Trousers never met my shoes, turn ups were a dream I could never realise, and sleeves missed my wrists. If a shirt or top covered my whole arm the body of it drowned me...I even did a course in fashion desing hoping that I could then be able to make things to suit tall thin men.
The thing you need to do is, IGNORE FASHIONS.
There is a huge difference, between being fashionable and well dressed.
Some people follow fashions, what people like you and I need to do is find their personal STYLE.
So, this means thrying on a hell of a lot of clothes hoping to find what shapes suit you best, and then finding them in shops you can afford...nothing than finding the perfect shirt when it's $125! Oh and take a GOOD friend, one who you can trust- not someone who'll say yes to everything and not one who isn't interested in clothes.
When you know what shapes and things suit, you just keep on buying them, if high waists come in and they aren't for you, keep wearing your trad fit, It looks so much better than trying too hard and looking a tit!
Keep in trend with colours, so this seasons "Yellow", might be the colour you choose rather than this seasons, voluminous trouser shape which might not work so well for you. By doing this you look fresh and with it, without losing your personal style.... D'you get me?
Stick to this idea and you wont go far wrong. For sexy- and you are- slim guys like you, a slight flare helps the leg, and looks cool; to keep the upper body looking less slight with layering, long sleeve tees under another short sleeve tee-shirt with perhaps a check shirt over that- (it's autumn, it'll look great). Layering is a great way of decieving the eye into seeing a bigger frame and making waists and arms look blurred so the "thin-ness" isn't so apparent. It's all about fooling the eye... Paler colours make shapes look larger, dark look smaller, (a small black fitted shirt will make you thinner....)
Baggy clothes should be avoided, when the wind blows and your frame's revealed, you look thinner, tucking in shirts I'd say is possibly not great, I have really long legs to my torso I wear a 34" inside leg... a shirt hanging over my waist, decieves the eye as to where my waist actually is (about three inches below my armpits) , and the layers of t-shirts add to the illusion. These clothes are aiding people's view of you however, you are not hiding in them!
Skinny clothes, ie, drainpipes will make you 6'9", which is great if that's the look you're going for but if not relaxed is better.
Honestly, the thing to remember is that 85% of the western world is dieting to achieve your frame and look, enjoy it while you got it! By your mid thirties you'll be singing a different song!
Good luck.
Anyway, the shirt at least should be form fitting...
