Soothing a 1 month old infant?

i have a 2.5 and 1 month old. i realize that she's only a month... and that this will get better... but ever since she was a few days old from 10pm to 1am she's very hard to sooth. i've checked whether she's hot, cold, diaper, full belly, gas drops, rub belly, legs, arms, head etc... swaddled, unswaddled kept her awake before hand...probably some other things. she is completely content all during the day and the rest of the night. i'll take any suggestions.... Thank you