You can't just 'get over it and move on'. As you say, your OH has an adult life outside the home and does not/cannot see that you are stifling without one. Is moving house really the solution? It's a very stressful process in any case, and you would still be in the same situation, just with mum/dad/sis nearby. I went through PND living 10mins away from my parents and in the area I had grown up in. Yes, it was good having someone around, but it was not what pulled me through.
I think you've put your finger on exactly the problem - having no apparent identity other than as someone's mum. If you don't want to go down the pills route, fair enough, you don't have to. Just having the prescription there can be a sort of background crutch - you know you can always go and get it filled if you don't manage to turn things around by different means. Nothing second rate in taking pills, that is merely one among many strategies.
First step: tell yourself, remind yourself regularly that your opinions, feelings, attitudes count. So do your needs.
Second step: does your child have any regular daycare? If not, then put him in a nursery for a couple of mornings a week. Those mornings will be sacred 'me-time' for you. Not for catching up on housework or going shopping, but for going to an Adult Education class where you can exercise your mind and talk to others interested in something other than toddlers. Some Adult Ed places also run registered creches for students' children.
Third step: carry a paper bag neatly folded away in your handbag. If you feel a panic attack coming on, stop what you're doing, take the paper bag and hold it over your nose and mouth. Breathe easily in and out inside the bag for a couple of minutes. Panic attacks may be triggered by the mind, but they cause real changes in your body chemistry, which perpetuate the attack. One of those changes causes hyperventilation. Paperbag breathing stops the hyperventilation and can therefore stop or ease the physical symptoms of the panic attack before they get overwhelming.
HTH, and hope also that others will be along soon to give you more support and advice.