This is probably going to sound tactless and glib and I know it sounds much easier than it is... It took me a very long time to work this out.
But you HAVE to become comfortable with yourself as a single person before you can ever find happiness with someone else. If you're looking for another person to fill the gap it will never work.
a) because you will always come across as needy and lonely, deeply unappealing characteristics which will put people off wanting to be with you
b) more seriously, because you will struggle with proper boundaries and will tolerate things you shouldn't
It's not easy by any stretch of the imagination but you must do some work to get to a place where you are happy being single or you will never find proper happiness with anyone else.
Key to it is to keep in mind all the time that the number one reason you feel that being single is undesirable is because society is shouting it at you. Economics and many years of patriarchy make women feel that things are better with a man and they are really really not. You may not accept this now but if you keep repeating it to yourself it will go in.
Get some counselling or therapy. Go on a retreat. Learn to spend time with yourself and to like yourself.
Being happy single is the key to life. Only once you've accepted that will you ever find happiness with anyone else.