Four month old sleep

My daughter is four months old today. About a week ago we went through what I think was the four month regression. She was getting up every 1-2 hours. She has never slept through the night but she also never woke that frequently. Then last Friday when I put her down at 7 with her last bottle she was sleeping til 1-2am without waking. And then getting up at 6:30 for the day. While still not through the night it was better than ever bc she was sleeping those long stretches. I chalked it up to the regression didn’t last long luckily - only about a week bc then her sleep improved dramatically. Well, now here we are a few days later and don’t know what’s happening. She’s up every 2 hours again and I’m exhausted. I tried to see if anything happened differently yesterday- she seemed more tired than normal yesterday and she took a nap at 3:15 pm and was still sleeping at 6 and finally woke up. I didn’t want to wake her up so I let her sleep. Could this be what caused this?? She usually goes to bed at 7-7:30 so maybe I let her sleep too long? Really praying things go back to the way they were tonight. Sleep deprivation is exhausting. She’s my only child and I’m really struggling with all these changes. I’m 40 and always slept 8-10 hours a night. I don’t know how all you mamas do it but you deserve an award. Especially bc I work part time, it’s so hard to function on so little sleep. Like I said things were better lately with her sleeping 6 hours at a time so could the late nap have thrown it off? Or maybe it’s the leap again? Or a growth spurt.