My son didn't eat solid for the first year as he wasn't interested , he stuck to breast milk . There is a mantra saying ' before they are one , its just for fun' so I wouldn't focus too much on trying to get him to eat if he is happy with milk but of course I am no expert so its good to speak to your GP. My son has allergies so had to be careful with some food as he does get stomach ache , culprits like dairy , wheat , fruits etc was too harsh on his stomach , he was tongue tied too but had that snipped at 3 weeks old . I hope you get it sorted . We were referred to Kings Allergy dept .