My 11 week old baby keeps vomiting sometimes while eating or after eating. Is this normal?

Very common. 3-4 month old can often regurgitate their food/milk without effort..It is a rather bothersome sight for parents/caretaker to witness. Nevertheless, as long baby is not uncofmortable, still eating and gaining wt, then i would not worry much. Don't over feed and thickening the milk with rice cereal etc..May reduce this a bit. Also, burping baby to reduce large air bubble in tummy. Good luck.
Reflu. Sounds like reflux. Has he always been a spitter. If so it is not unusual to increase around three months of age due to swallowing more saliva. Talk with your doctor about reflux.