Filling days can be hard and it's probably a good idea for both you and baby to have a routine. Organize your day however you want but it should probably involve the following activities :
- Bath time (at this age it's clean baby and out, but as soon as he can sit on his own reliably you can leave him in a bit longer and include bath toys)
- Play mat time ; baby needs to exercise, learn how to reach, grab, roll over. It's a good idea to get one of those thingies you set over the baby with toys he can reach (those with music, texture and shiny usually are most interesting to baby)
- naps : baby usually need two naps a day, after 2-3h of being awake. Use that to nap too.
- when doing housework, try putting baby in cosy where he can see you. They usually like the cosy because they feel tightly held as in the womb.
- try a pacifier. All babies are different. My eldest didn't need one, my youngest would have left me dead from sleep deprivation and deaf from all the screaming without the pacifier
- try to go out with the pushchair for a couple of hours everyday. Fresh air and sun is good for baby and will tire him out, and usually they like being out in the pushchair. It will also be good for you to be out of the house. Go to the park, or shopping, or to buy groceries, or to have coffee with a friend, whatever.
- You can also hold baby while sitting down and doing something else (watching tv if that's your thing, doing stuff on your phone, whatever. It can be a quiet cuddle time where baby is happy to be held and you can rest mentally as well).
They are heavy little buggers, aren't they ? I feel like my biceps doubled since I had my eldest. Sling is one option but it's a temporary fix as he will get bigger in no time. I would just try to get him used to not be held all the time.
And also, the one tip I needed the most as a single parent to two young kids ; it's not the end of the world if he's crying and you leave him crying five minutes. So long as he is clean, fed and safe, no harm will come from letting him cry a couple of minutes. (And it's not like I can make his bottle while holding him at the same time, anyway). My point is, you don't need to put him on your shoulder the very second he starts to whimper.
And before I get lynched : obviously I'm not saying you should ignore him if he cries, but if he wakes up/starts crying and you need a minute to fix his bottle or you were in the shower and you need a minute to step out and get dry, that is fine.