Exhaustion- is this normal?

I have a 3yo and a 6 week old. I primarily wake up with the 6 week old throughout the night because my husband is back to work and he wakes up with the toddler in the am.

My six week old wakes up once a night between 3-4 or 4-5 to eat, change diaper and go back to sleep. Sometimes wakes fussing for his pacifier etc.

My issue is that I feel constantly exhausted this week, tired and having issues waking up and getting my day started. I feel like I have to force myself out of bed.

I sleep from around 11p-3a and then from 4a-7/8a. Shouldn’t this be enough?? I usually wake up once around 1:30a to give baby back his pacifier.

My six week old gave me a 7hr stretch last night and I still feel exhausted. Have I just not caught up on sleep?

Is this normal??