4 month sleep regression 😥😥😥

Is that what I am going through?? She is actually 3.5 months but cries soooo much and so intensely lately when we try to lay her in her bassinet. Previously she was sleeping 6 to 10 hours straight each night. We don't lay her down drowsy because she screams as soon as she hits the bassinet. I have no idea how anyone is able to do that. She also tends to breastfeed to sleep. Is that bad? Her bedtime routine is pretty consistent albeit sometimes an hour or so off here or there since I've gone back to work. She wouldnt leave my arms last night not even when my partner held her she screams terribly. She was even extra fussy when I came home from work and didnt want to play like normal. We are just so tired and overwhelmed. What if we cant sleep train her correctly will she be like this forever? Tips please