When shall I tell my best friend I’m pregnant?

Me and my best friend have been friends for over 15 years and tell each other everything!!

I’m currently somewhat avoiding her as I know I won’t be able to lie to her. As ttc is usually a topic that comes up.

My friend has been trying to conceive for the last 4 years and has really been struggling with mental health because of it.

Me and my husband started trying last summer and had a devastating miscarriage last October. We are now 5 weeks along and have known for over a week but I am worried constantly that I’m going to miscarry again.

Please can I have some advice on when I should tell her?