Most Helpful Girl
If it makes you feel any better, 18 is still pretty young and a bunch of people around your age can relate. Basically, you shouldn't feel self-conscious about it because it's pretty normal.
You kinda have to put yourself out there and not be afraid of rejection. Meet people at school or work, go out with friends more, join clubs, volunteer, use a dating app, etc.
Most Helpful Guy
There is no formula as such. You need to keep trying, I don't know make some female friends to start with, go on some dating sites or something.