Pregnant. United health care? Medicaid??

So I recently found out I’m pregnant and I’ve already made an appointment at my local clinic to get a blood test for free, I’ve already had it confirmed by a doctor that I’m for sure pregnant. I’m only 18 and I’m still under my moms insurance (United Health Care), I haven’t told her I’m pregnant yet and I want to wait until after my first ultrasound so I can give her a photo. I’m concerned because I have the insurance card but I’ve done some research and seen that some people mentioned that prenatal care and l&d was not covered under their parents insurance. She works for united health care (work from home), so I’m not quite sure what to do now. Should I just find an OB/GYN that accepts united healthcare and take money with me Incase they don’t cover the ultrasound?? My friend mentioned applying for Medicaid but I don’t think I’ll be approved because I live with my boyfriend and his parents and they make a pretty decent amount of money, which I don’t know if that has anything to do with it, but we’re just living with them at the moment until next month (we’re getting our own place). We both have good paying jobs but insurance is a must, especially for l&d! I’m not sure how all of this really works and I’m so stressed. Any advice helps!!!