Kelly, there's no such thing as overreacting or a silly feeling. There's feeling what you feel, and there's nothing wrong with that. That being said, there are different ways to deal with how you feel.
If my sympathy (empathy?) counts for anything, I understand. I don't talk to my parents, either, and you know it can be difficult talking to anyone else.
Is there a way you can move in with your parents? Perhaps being away from your ex would help. If not, find a job or hobby somewhere else where you might meet people who are interested in the same things, or just a nice person to get a smile from. This could be a museum, bookstore, favorite store, etc.
And if you can bring yourself to it, a counselor could help. Dealing with all that by yourself must be a real heavy load on your shoulders and heart.
Or, if you can't do that, would a journal help? Russian girls traditionally used to keep dolls called "worry dolls" that they would tell their worries and thoughts to. Even if it's an inanimate object, it can help. Beyond that, if circumstances allow, a dog or cat (if you're nice to it) would be a great option. Look into local shelters for a friendly dog who likes attention, and you're sure to have a companion.
I'm sorry if this doesn't help, and that you feel so awfully.