OK, you made the first step. Asking for help.
Now where is Help available?
IMO the best place is some professional help.
I think this is beyond support, and you should be look for more advanced help.
We only miss what could have been. I know I don't miss what it really was.
I popped the words "I don't love myself" into search and several links came up. Maybe you can do that, too.
A professional can help you dig deep into your core issues and draw out memories. Seems to me, from all that we've talked about here, many of our issues arise from childhood...perhaps someone in our past someone made us feel unlovable or unworthy.
And, there are loads of books out there to get started on your own.
Taking up activities/projects that give us a sense of sense of accomplishment and self worth can lead us to self love. I believe these are some of the ways and means you'll find your happy.