Baby unhappy all the time 😞

The past 3-4 days I can’t seem to get my 4 month old baby happy. He fights on nursing and when he does eat it takes him forever. (45 minutes) and even after these long feedings he just cries and cries until he’s willing to eat again. I’m so miserable having a non stop crying baby. The crying is getting to me, I’m getting angry with my baby, and I feel like such a horrible mom not being able to have a smiling happy baby. Will this pass?