Hello and hope you are doing well.
Your symptoms could be due to food allergy. More so if you have introduced anything new into your diet. Maintain a diary and note down and monitor your symptoms. This may help to narrow down the search. It could also be food intolerance, both food allergy and food intolerance can cause symptoms of nausea, vomiting or abdominal pain. The difference being in food allergy the IgE antibodies are increased. If symptoms are acute it can even be due to an infection, gastroenteritis. So, if your symptoms persist consult your doctor for an evaluation.
Hope this helped and do keep us posted.
I am lactose intolerant, try not eating any dairy at all for a few weeks then try some see if during the couple weeks it goes away.
Or just start paying attention if you see you get sick when eating diary probably is the diary.
Also try some lactose pills see if it stops the sickness they help me but note it doesn't for everyone.
Btw you should never only eat protein that is horrible for your body!!!!