Can baby be allergic to my milk? she projectile vomits 5min after she drank, sometimes while she drinks. doesnt happen when she drinks lactogen, only when she drinks my milk (been on a mix since 2 weeks old, she is now 12 weeks)

Unlikely: Infants are rarely if ever allergic to their mothers milk. They can be sensitive to something from your diet that filters through, but it seldom produces dramatic vomiting. If anything the cow milk solids in the formula is more likely to trigger allergic issues. You may want to find a breast feeding coach to see if there are techniques you can use that can help avoid this.