HI,
I have taken SSRI's on and off for about 30 years......... 15mgs is a really low dose. MOst start on 20mgs, so i would imagine you'd get very little relief for the anxiety and low mood on 10-15mgs. and it can take up to 6 weeks for them to kick in properly
I take 30mgs at the moment, but have been on 60mgs severa.l times over the years. Before i started HRT i was on 60mgs and it really helped with the night sweats, but not the brain fog etc
I am on HRT as well now (femeston) and find both together are a pretty good combo.
There are no 'perfect' regiemes and seems to be a lot of trial and error and see what suits you.
Once your anxiety and mood improve you may well find HRT does okay with you or maybe not, but you'd have had least a go.
As for the headaches- it is probably a combo of things, stress!, new meds, meno; pesky, but will improve as stuff settles.