I want to be an diagnostic medical sonographer.?

I am interested in being a diagnostic medical sonographer. My concern is that Im going to graduate college with a bachelor's degree in university studies (like general studies) in may, I plan to be an occupational therapist and get into grad school with the cles I took, and I have a fear of not finding a job for myself and my baby when he's born and I wanted to know If anybody heard of someone holding a bachelor's degree in one thing and getting their ociate's degree afterwards or would I have to get a certificate in diagnostic medical sonography? I really want a job to help support my son and for myself first then grad school when I get the chance.