Hi,
Keep a diary of your symptoms,often it will show a fluctuation linked to your menstrual cycle if it is linked to your hormones which may support your argument that it's not a depressive illness that needs anti depressants.
I would maybe print out a copy of the NICE guidelines for your GP and read them yourself if you haven't already,there's also a lot of other info out there you could take to your GP to support looking at starting HRT if that's something you want to try.
If you get no help or it's beyond their understanding you could ask for a referral to a menopause clinic.
I started being peri menopausal in my early 40's and didn't do anything about it,at the time there wasn't really all the information available that there has been the last couple of years.
I always had bad PMT but was getting lots of worsening symptoms,fatigue,mood swings,lowering libido and palpitations which I had all kinds of investigations for and nothing was ever found.I now realise it was peri menopause and really wish I'd realised sooner as I wasted so many years.
I had a supportive GP but we just didn't relate it to the peri menopause at the time and didn't until I was in my late 40's.
I only realised and asked my GP specifically about peri menopause when my periods changed,shorter cycle and heavier.
My GP was great and started me on HRT but it soon became obvious I needed to go to a specialist at the menopause clinic as it went beyond his knowledge.I've always had issues with my hormones and now realise and been diagnosed retrospectively with PMDD.
My advice,get as much information as possible ,keep a record of your symptoms and fight your corner if you do feel it's the start of peri menopause,don't wait if you're feeling bad as it's just wasting time.