I hope you are not giving concentrated milk. Means less water and more powder! Don't worry. Since you havealready started top formula feeds, start banana mash. It should be just right not over ripe. First time start with small piece ie one third banana, middle piece,mash it with proper cleaned and rinsed with hot water. Feed the baby with spoon.while baby is in supine position in your lap or on bed. Feed it little inside mouth otherwise it may be thrown outside. The will swallow it nicely .Inbetween keep talking to baby. You can add a spoon of breast milk to make semisolid. They love it. Slowly go on increasing the quantity of banana.I am very sure he will respond and do well. BANANA is very good food. It has nutients, minerals, fibre and probiotics. So no worry. Otherwise I am always there.
Next Steps
I am sure it will resolve. I am there .Breast feeds
Health Tips
Breast milk is best. But don't stop top feeds since you have already started.