Massive hugs to you. My LO is 10 months but it feels like I was were you are only yesterday. My DD went to sleep like a dream so I hoped number 2 would be the same, but no such luck at the start. He too went to sleep no problems throughout the night but the day was horrible and with 2 yr 5 mth old
Dd racing around...argh
Like someone else has mentioned some naps (where possible, like dad home) I would hold him through some sleeps to let him catch up but then his other sleeps I just always kept to the same routine and always attempted to put him down awake. Would really listen to his cries too as sometime it was more whinging and if I left him for a little bit he would drift off. If really crying I would go in. This would often result in re swaddling him and then placing him on his side and shush patting and quite often he would prefer to sleep this way, even though we know back is best, I went with him. I can't tell you much else than that really, it did come right but I think a switch flicked at bang on 3 months and he has been an awesome sleeper since, probably a better day sleeper in the end than my DD.
It is so nothing you are doing wrong! Be kind to yourself. I bet myself up about getting it right way too much, esp as it had been so much easier with number 1. If they are sleeping well at night and self settling we know they can do it, but when so young we just need to help them a little through the day. No crying over the cot like I did whilst also trying to shush/pat, wish I had not beaten myself up so much!
Good luck