u just have to go to a party and meet people just go up and talk to them

Buff up a bit.

About a guys look I never talk. Whether girls/women are attracted to your look in some ways, I can't tell. Even its not my biz.

Since you can make compliments, means that you're not taciturn or such.

So your problem seems to be the lack of (self?)confidence and being introverted some times.

Technically, it seems a problem of your personality. But I think it would be foolish to define this that way, because both character traits are only a small part of your personality.

I guess your problem is specific. You've to get more confidence or trust in women. With more self confidence the problem with the partial introversion should solve itself.

The only question I've in my mind is, if you've the right girls/women in your focus. Women/girls that correspond more to your personality.

But this is a other prob and you've just to find it out yourself. This requires a huge amount of life experience that, tbh, I haven't got yet.

Confidence, something you should have. Not only with a female but with all the people that surround you. You lack confidence, your body shows that, when a girl looks at you your body says ''Lack of confidence here''. That's the truth, used to have the same problem.
Anyway, read some books on how to increase your self confidence and how to behave in public. Search for Body Language books, good luck.