I don't feel it's silly or childish of you at all to want reassurance from your therapist, that's part of why we hire them! It's normal to become attached in many cases and that actually can help the work get done better, the issues to resolve, but it is agitating to deal with the attachment and fear of rejection or loss, I know. I also do therapy online.

Does he know he's supposed to respond to you at this point, or could he be waiting for you to initiate contact? Many therapists, including mine, won't normally intrude on clients by reaching out, they won't initiate contact, so as not to pressure the customers or impose their own wishes on them.

I hope you can find the courage to tell your therapist that after talking about the difficult subject of self harm, not hearing back from him worried you. Perhaps you can just start that way, and ask why he hasn't replied yet?

Anyhow, I can empathize and I'm sorry you're struggling with this right now.