Baby gaining weight but dont eat a lot

Na

I had a 8 shift today and come home to notice that my LO only ate 6 oz all day. I breastfeed when I'm home and pump at work. I noticed that when he drinks from the bottle, he gets distracted or bites the nipple instead of eating. He is approx 14 pounds and it's almost 4 months. on his 2 month appt he was 12 pounds. We tried like 4 different bottles already. Dont know if it's a leap or what