Breastfed babies nearly always poo at least twice a day until 8 - 12 weeks and then it can drop off. It looks like your DS is less than 8 weeks old, so not pooing daily can sometimes be a sign of insufficient milk and it could also be constipation from the formula. Or it could be neither of these things and he's just slowing down earlier than average. How are the wet nappies going? And the weight?

I agree with MadB that fussiness in the evenings is very common. It is not a sign that you have low supply. Babies seem to need comfort and extra food at that time of the day - to wind down after the day and to tank up for the evening. You will find toddlers become fussy at that time of night too (it's not called the witching hour for nothing ) and even school kids tend to come home in the afternoon and eat up a storm. Your breasts are always making milk, even as he's sucking, so even if he is feeding constantly he is getting some milk. Many mums find it helps just to spend that time on the couch or in bed feeding and not worry about doing other things for that time.