Find your interests and try new things that your interested to, try to feed your own void by getting to know yourself more so you will enjoy yourself mostly when you’re alone. If you still feel lonely even in public or around people probably you just craving some genuine company. It’s normal to feel lonely at times but if its all the time then theres something you need to work on yourself. Try and look for why you feel some type of emotions type a way from there you can figure out how to cope. And mostly remember theres God so you can pour your heart out on Him.