Mourning relationship after birth

My husband and I welcomed our beautiful baby 6 days ago, I love her so much and feel so blessed to have her. Last night things got a bit too much and I'm not sure if it was the lack of sleep or hormones but I just felt so devastated and couldn't stop sobbing. Like I love my baby and I feel so lucky to have her but I also feel so incredibly sad that our lives have changed forever now, its like im mourning our old relationship, just us two. We've been together for 8 years and have done whatever we wanted in that time, travelled, had a lovely life together. I love my husband so much and watching him be a dad has made me love him even more. Is it normal to feel this way? It's just not how I expected to feel at all. He comforted me and reassured me that I'm just tired and we'll be perfectly fine but my god I just felt so incredibly sad.