First, 

You are not alone. Truly. There are millions of women around the world feeling exactly as you do right now, even if not all of them say it out loud.
Motherhood isn’t all rainbows and roses. It stretches you to both ends of every emotion you can experience as a human being. If you think about it psychologically, it can feel like your sense of self cracks open, your identity shifts as you give so much of yourself to another person. That’s especially intense in the early months, but you do gradually find your way back to yourself as time goes on.
If your baby is around five months old, you are right in the thick of one of the hardest phases, the big sleep regression. Even with a relatively “good” sleeper, that period can feel unbearable. I remember being up at 3am, rocking my baby, nothing soothing him, my body aching from exhaustion, still feeling disconnected from my body after a C-section. I remember crying quietly and thinking, wtf have I done, this feels like torture.
And then morning comes, they smile at you, and somehow your heart softens again!
For what it is worth, I don’t think we are mis-sold motherhood but I do think we remember it differently. Time softens the edges. The exhaustion and relentlessness fade just enough that what stays are the moments of love, the tiny smiles, the feeling of holding them close. That doesn’t make this part any less hard while you’re in it. It really bloody hard.
That’s the strange truth of it. Parenthood is constantly changing. Every phase feels all-consuming while you’re in it and then later it becomes something you look back on differently. A mum with a toddler might remember the newborn days with softness even if they were incredibly difficult at the time. I already look back at photos from those early months and wish I could hold him that small again.
I won’t sugar-coat things. In some ways, it can get harder as they become more mobile. Crawling, pulling up, walking, weaning, it demands constant vigilance. And alongside that comes the endless cycle of cooking, cleaning, washing. It can feel relentless, like you’ve lost control of your time. No one warned me about that. In some ways, you are giving yourself over completely for a while and as many people on this thread have advised, accepting the situation
for what it is will help.
Not sure if this is useful but I’ve noticed a pattern in my own experience. The first couple of weeks after a developmental leap can feel incredibly stressful and draining. For example, when my baby learned to pull up at around 10 months, that was a really hard week, constantly having to watch him and catch him from falling. I remember thinking, I simply cannot do this. I felt so overstimulated. But then it becomes your new normal and things settle for a while before the next change comes. It feels like a cycle, intense, then manageable, then intense again.
Try, where you can, to carve out small pockets of time just for you. Even something simple, having someone watch the baby for a short while so you can lie in a dark room with a cup of tea! Watch your favourite film in 15 minute chunks if that’s all the day allows. Write a few lines in a journal while they nap. These small acts don’t fix everything but they help you stay connected to yourself.
Also, even though things feel bleak right now, try to cherish the small moments as they happen. That smile, that little laugh, the way they look at you like you are their whole world. These moments pass so quickly even though the days feel long.
If any of this feels heavier than you can carry, it’s so important to lean on the people around you and speak openly, especially about the possibility of postnatal depression. You deserve support.
Unlike others I think being close to your mum at home right now is the best place to be. You’re not meant to do this with no network. Paris will still be there OP. That life you imagined hasn’t disappeared. Try to picture yourself one day walking those same streets, this time showing your child the places you love. That version of your life is still ahead of you 
Right now, your baby is tiny, and humans are born incredibly dependent. Because of how we develop, human babies need far more care and closeness for much longer than most mammals. You’re in one of the hardest chapters. Take it one day at a time.