Too much milk????

My baby is 14 weeks old. He just started drinking 6oz this week because he was still eating every 3hrs with 5oz so we increased it to see if he would last longer. Well, we could last about 3.5hr-4hrs.

I guess it makes me worried because my neice is 9 months old and takes 6oz too but lasts longer in between feedings. My doctor said as long as he doesn't spit up or have belly ache, it's okay.

He eats every 3-4 hours during the day and sleeps from 9-6am.

Am I feeding him too much? He is formula fed by the way and some thawed breastmilk every now and then.