Yes, I’m afraid it can be “this bad”. You gave your heart away. You probably had ideas about your future together. Now you have not only lost the person, but you’ve lost that entire imagined future. You are grieving both. It’s also a blow to your self-esteem that someone you valued didn’t return the feeling. It’s a lot for anyone to deal with. Often it takes more than 6 months to fully recover.
That being said, it’s important to remind yourself that there are millions of people in the world and your ex is not representative of the rest of the human race. Her judgment that you are not what she wanted doesn’t apply to everyone. There are other, probably more suitable, people out there who will love you and be delighted when you love them back.
Please understand that your feelings are not at all unusual. With more time, they will probably fade. If they don’t, it may be that you remind yourself of how devastated you were as a way to avoid risking romance again. I would find that very sad. You deserve to find a special person who will love and cherish you. But you won’t find her if you allow fear to keep you from looking for her.
If you are still feeling so distressed and scared after another few months, I hope you will consider seeing a therapist for a few sessions to help you.
I wish you well.