Hi L.,
When you are burping your son, are you hitting his back? If so, you might try just rubbing his back. That always worked for my children. I hated the pounding on the back, and all of their little limbs twitching with it. I just rubbed, with their head on my shoulder. It works just as well, and it soothing and sweet to them.
Days and nights mixed up is normal. Remember that the entire time he was in your womb, he was rocked to sleep all day long as you walked around. But, when you rested, he could wake up because he wasn't being rocked anymore. I have always thought that is why they mix up days and nights. Have you tried to wear him? I would get a baby carrier of some sort and strap him to you, being careful that he is safely not suffocating (some sling carriers have this risk). And, I always co-slept with my children. I always had a good night's sleep (well, mostly anyway). Five weeks is still so tiny.
Sex drive, well that can be normal. But, you aren't even at the 6 week point yet, which is typically when they recommend resuming relations with your husband. Give it time. With some babies it took more time than others for me.
And, your body is still healing. The bathroom thing should repair eventually. I'm not sure how much trauma your body experienced during labor and delivery though. You could ask you doctor about it at your 6 week checkup.
Congrats on your new baby! Such exciting, exhausting days!