Some days, and hours of the day have felt similar to me.
The ceaseless list of things to do around the house, and my DH's attitude and expectations frequently have a real impact on how I feel, and this is before I add caring for, and entertaining my 2.7 year old DD to the mix (which I love, but dealing with toddler behaviour is deeply draining).
I have done every single night feed, and have solely cared for my DD at night during teething, illness and nappy changes, as my DH is deaf and would not wake if she was screaming the house down. My DD still wakes at least once per night (such as now), and wakes early in the morning. I have no support network (my parents would love to help, but are nearly 2 hours away and have other commitments too), and my DH works long hours and also spends time on his hobby at least 5 days a week which fucks me off, but he refuses to cut down. My appearance has also changed so much too - mainly my face. Looking at a photo before and after I gave birth is like looking at two different people.
I find parent and toddler groups unbearable, and they make me feel more isolated. It really helps me though to try and make sure I've put my make up on, and am washed and dressed by 10am every morning. Sometimes I have to force myself to go out, but just taking my DD to the corner shop/local shops and chatting briefly to the staff, or going for a little walk, or going out in our communal garden is really beneficial for me.
I love Autumn, and really enjoy taking my DD out to look at/talk about the changing colours and falling leaves etc. We take carrier bags, and spend ages collecting conkers and leaves etc, and she splashes in the puddles and rustles and jumps through the leaves. We then do lots of printing and painting and crayon rubbings from them at home, and will make a conker wreath or garland this year. It cheers me up to see my DD enjoying herself and when I see her artwork.
Try to grab at least 15 minutes of 'me time' every day, and try and take pleasure from little things (a lovely cup of tea and a biscuit or two, a glass of wine, reading a book or magazine, looking at/stroking cute dogs in the park, catching up on a favourite programme, a chat with a friend/family/neighbour, a bath, styling your hair differently etc).
Try and get your husband to look after your DS whilst you go out for a walk or go to the shops or for a coffee, and try and make it a regular thing. We had a dog when I was growing up, and my Mum told me that every night straight after dinner, she'd bolt out the door with him and walk for 30-45 minutes, leaving me with my Dad. She said that was her bit of sanity and normality for the day, and sometimes she'd cry with relief during the walk. I didn't understand this before I had my DD, but I really do now.
If you've tried doing similar to the things I've mentioned and they're not working for you, please, please go back to your GP. Ask to see a different GP if possible. You should not have to suffer when they have the means to assist you.
It's so hard not to think about your marriage and husband, but try your best to block it out and focus on you, and looking after yourself. This is what I have had to force myself to do, and it is very helpful for me.
I wish you all the very best 