Wow. This post is overwhelming enough to trigger my anxiety. A few things hit close to home.

Let's try to take this in steps. I know the feeling if oncoming anxiety. It's awful. But you have a chance to try some coping skills before it gets too bad. Take some time for yourself. Ignore some housework, take a hot bath, go for a walk, listen to music you find soothing. Just breathe and slow your mind down. Do you have a therapist you can call?

As for the other things in your post. Flat out ask your guy if you two are exclusive or if he still wants to see other people. You are in the relationship too and have a right to know.

Talk to your 13 year old. Even if your ex doesn't say anything he will pick up on the stress. Be honest, but let him know everything will be alright (even if you don't believe it yet). Kids think their parents can fix everything. He doesn't need to worry.

Remember how you felt two weeks ago. You will feel that way again soon. Good luck. Messege me if you want to talk. I know how you are feeling.