You poor thing, just know you're doing a great job
I have a 4.5 month daughter & I'm in no position to offer advice as I'm still learning myself but she's had a sleep regression too which is so frustrating!
She's gone from waking once a night to about 3-4 times (seems to differ each night).
I used to put her down to sleep at 7pm but lately I've moved her bedtime earlier & it seems to be working ok for us. The days where she is super cranky I've started the process of bathing her at 5.30pm, then dress/swaddle her, feed her & she seems to go to sleep after having a feed. I don't know why but for us moving it forward seems to have made the world of difference although I'm probably creating bad habits.
I say trial & error & do whatever works for you & your baby. It can be so hard when they don't sleep well particularly during the day. My poor dd will get really over tired during the day & fight sleep. Some days she'll fall asleep in my arms & others I'll put her in her cot, she'll get upset but then finally falls asleep. I usually don't leave her for long though & some days I'll put her in her pram around the house & she sometimes goes to sleep too