Great to see you on the beyond blue forum and I know that by reviewing some of the threads on loneliness or social anxiety, you will feel less alone. Many people lack social connections to make them feel fulfilled but there are many strategies that you can take to help with loneliness. As Pepper has mentioned there are some ways to get support such as going to a headspace centre near you. This service often has a group that is purely for socialising. It would be a good place to check in. If you get an assessment there they can also refer you to social groups around your community as the centres are typically well connected.
Another avenue is attending your local library or community centre and asking about groups that occur. Often, if the groups are open, you can do a trial first.
Another avenue to increasing your socialising is taking a course, getting a job or volunteering. Places that have a big pool of staff such as hospitality work or a health care setting may open you up to meeting more people.. By exposing yourself to a group regularly you may find some people that you click with.
Another way is to be more assertive with your old friend group from high school. They may attend some groups or events that you can attend which may expand your horizons.
The transition out of high school is a difficult one as your independence is growing and friends are all going in different directions, some to uni, some to TAFE, some may move and some may go into employment. Finding your own unique path can take time so be gentle on yourself. If you are really struggling to find your path, then I would recommend a counselling session either via the headspace centre or you can visit your GP. Another option could be to talk to an adult that you feel comfortable with and ask then for some help to find social avenues that will increase your connection with others.
If you ever find your self really stressed out with no where else to turn, call the beyondblue support line on 1300 22 4636 or the Kids HelpLine on 1800 55 1800. You can speak to someone immediately and they can help you get through difficult moments and work with you to find some solutions to how your feeling.
Wishing you the best possible outcome,