I think I get/got these symptoms when my hormones were quickly fluctuating. I never had any pain until I got pregnant for the first (and only) time and then lost the baby. Within weeks, all the pains and weird symptoms started. Looking back, it must have been the hormonal upheaval which triggered things. People kept saying it was caused by depression/anxiety because of what I'd been through, but I knew in my heart that he pain was far too severe for it to be psychological. Besides, I started getting water retention on my ankles and I dont think the mind can do that!
I do recall, each time I've started a new HRT, I've noticed the pains in the same areas I had them before (though nothing like as severe as they were originally, when they'd wake me up at night). This is why I think it's fluctuating hormone levels rather than low levels per se. It also explains why, on the pill, when your own hormones are suppressed, I feel better than on HRT where you are topped up so can still get fluctuations.
I think one week of HRT is very, very early days. At best , all that is happening are your hormones moving about (up) a bit. Whether it's a side effect, or would have happened anyway due to low estrogen, you wont know until you give it a fair trial. I nearly gave up at three weeks, but lots of people on here told me that was miles too soon for side effects to go and the HRT to work. My new GP has since confirmed three months is the minimum you should give it, unless the side effects are unbearable. I would say it was six months before I felt more myself again.