My LO is 5 months today. He had a good 4 month check up, weigh at 15 lb 15 oz (50-75%). However, his weight has been stuck / fluctuating at 16 lb for the whole month. (we have a scale at home). That put him at the 25%-50%.

We are exclusively breastfeeding. I nurse him exclusively during the weekends, and during the weekdays he gets 3 bottles of breastmilk from nanny, and 3 nursing sessions with me each day. LO had a few days of nursing strike just last week, but he definitely hasn't been gaining weight since the 4 month check-up.

Instead of growth spurts, he has more of a "non-growth spurt". In the normal days he would take 4-6 oz per feed, but the past 2+ weeks he would have taken 3 oz per feed. Then even though he had gone back to normal lately, he is still not gaining weight regardless of how much milk he's drinking. He would poop 1-3 times a day though and 6-8 wet+dirty diapers during the normal days. On the "non growth / slow days" he gets 5 wet+dirty diapers....

Is this normal, or should I be concerned?