When should I go for my first ultrasound/prenatal appointment?

Im not sure of my lmp.. It was either May 11 (on a 22 day cycle assuming it was a period, but it was short and light) or April 18. But when should I go for my first prenatal appointment and when will they give me an ultrasound? I really want to wait until 12 weeks since the risk.of miscarriage drops dramatically. When do obgyns typicallt do the first ultrasoubd and when should I schedule my first appointmenr?