hello akina1234,
your baby's weight is very good lar! I'm very envious of you!! My baby is also 4 month old but he only weighs 12.4 pounds. I should be the one who worries!!! but my doctor said we shouldn't be too concerned cause as long as baby is healthy and happy, it should be ok! He asked me not to start any solids for him until he is 6 month old. He said all he should consume now is just milk and water. He is taking 4-5 oz of milk 5 times a day (4 hours in between as well). you should be very happy about your baby's weight!!
My son has the similar problem. He is so reluctant to drink water, even I mix the water with juice and dilute it to 1:3. However, it still doesn't work. At last, I use the spoon to feed him water and he is willing to drink it, though it's not so easy. Actually, that's also a good training for him. After all, he should learn how to take solid food starting from 5-6 months. He is now 7 months old and he drinks water or juice everyday. Your baby's development is quite good. As long as his current weight can be double his birth weight when he starts his solid food and there is an increasing trend in his weight gain, it is a good sign. There is no need to worry about. If he refuses to eat anything, don't force him at the moment. You may try it later.