You really need to complete the second week of everyday doses, before you move to your usual weekly schedule. I wouldn’t imagine that this low dose would cause low mood, especially since it’s local (although a tiny amount enters the body systemically). You could be a natural worrier, especially about starting this treatment, and have just attributed these feelings to the Vagifem, as that’s the only thing you’ve done different this week.
I recall I just had a mild stomach ache once or twice in the early days. I haven’t had any other symptoms, and the treatment has really helped me, almost instantly.
Have a chat with your GP to put your mind at rest.