What you are feeling are the effects of a breakup. You should have healed and recovered by now. If you don't have many friends to offer emotional support, don't fret. You can heal and recover without external support.
You should tell yourself the relationship is over, you should stop thinking about her. Let your heart know that what's in the past is in the past, it's time to move on.
In the article, I have provided steps you can take to heal. I will advise you to read them again.
However, the most important thing to remember is that you've to always remind to focus ahead. When you think about her, snap out of the thoughts. You have to stop thinking about her.