Hi @Chris,
I have had a similar experience to you, several times. Please let me stress that you have done nothing wrong in opening up! You felt comfortable to share your feelings... this is a good thing, no matter how you look at it.
There is every chance you may still receive a reply from your friend.... not everyone checks their email every day... I know I don't, anyway. I guess with most people having smart phones these days... we just expect that everyone is always online, but that isn't always the case.
Sometimes people just don't know what to say and so they withdraw... it leaves us (people like you and me) in a kind of limbo which can feel very uncomfortable, especially if we are prone to anxiety.
For now, @Chris, try to distract yourself with something that you can do to help yourself. Remind yourself of all the possible things there are out there that can make you feel better. You might try calling a different friend or emailing someone you haven't been in contact with for a while. Or you might go to an exercise class, a walk in the park or coffee in a nice, comfy cafe. Think about the things you enjoy and plan to do them.
No response to an email is not a negative response, I aways remind myself. It's a completely neutral situation. You might wait a week or so and then maybe give that person a call. Or you might decide to look elsewhere for support. Either way, it's your decision and you are in control of the situation, even though it may feel that you are not.
This kind of thing has happened to me so many times. I find I get upset when I believe people are ignoring me. It's one of my issues. The fact is, people are just so busy with their own lives and they aren't trained to know how to respond to someone who is feeling low. It can be intimidating if you don't have the right words.
Are you getting professional support?