It might be, but on the other hand it might not. Considering all the ups and downs of our hormones over such a number of years, it's possible that your symptoms may just be a temporary blip.
Unfortunately, it seems, the menopause isn't something that's very well researched (well, from what I was able to find out) and when I saw my GP for advice, just about the only thing available were leaflets from HRT companies - nothing about dietary advice, vitamin/mineral supplements. Hopefully, there's better advice now, even though that was only 8 years ago.
As coco says, getting a hormone test is the first step. But please don't assume that your recent symptoms will continue for years'n'years. They may, but they may not. (Mine didn't.)
When I was coming up for the menopause there were other older women only too happy to tell me all the scare stories they could think of. For me, it seemed the most significant aspect of the menopause was stress - but my children where in their twenties at the time, so life was different for me.
As for your son, could I suggest that you explain your situation to him in the way you would if, say, they were recurrent headaches? Many 4-year-olds are likely to be able to understand those and the attendant grumpy feelings, without you having to explain the complicated gynae stuff.
And, no, you're not selfish at all for having a child in your 40s. You sound like a fabulous mum, and that's all your little one is concerned about.