kitkat sorry you are feeling so down. You are not the only person to have ever felt like this. I keep having moments where I feel like being a mother is just temporary and I'm just pretending. Dh doesn't get it. He is also out 12 hours a day and I feel like I make a lot of decisions alone. He's not super aware of the baby like I am. He could just sit and watch TV and not even notice that DS needs attention. I have to always ask him to do nappies etc. It doesn't help that I breastfeed either.
Have you been going to baby groups? It helps to talk to other mums in the same boat and knowing that we are all muddling through and just guessing. No one really knows what they're doing so they?!
On the calpol front j wouldn't give it just to see if it works, it is paracetamol, a medication and if there's no fever then is perhaps unnecessary. Of course, this is just my opinion, at the end of the day it's your baby so you choose. I try and focus on that a lot, my baby, my choice.
I'm not sure how closely I've followed your posts (there are lots of people here!) but on the sleeping front is it possible to co sleep in your bed? This has massively helped my sleep Deprivation and I don't care if it's a 'rod for my own back', my baby is settled and I get to have some sleep. My life was revolving around sleep and since I accepted its ok to have DS in bed with me its made a huge difference. We do it safely, firm mattress, no gaps anywhere, pillows and duvet well away from him. He sleeps so soundly, so I do to.
I hope some of this helps, you sound very unhappy :( please be assured we all have times where we think 'omg I've changed my mind, send the baby back!!' Not sure my dh will ever understand this, but that's how I feel. It can make me anxious at times to but I'm doing my best. That's all we can all do.