BCBS & Medicare

Is anyone knowledgeable regarding Health Insurance who has valid information on how having Medicare as well as blue cross blue shield insurance would work? I am 23 (F) who is pregnant (6weeks) and I am on blue cross blue shield insurance from my father’s employer, however they are denying me coverage for any pregnancy visits or medical appointments relating to my pregnancy. I don’t want to loose my BCBS insurance coverage but I have to get on Medicare because of the pregnancy. I have already applied but My main questions are: will my current doctors who only accept private insurance deny me for non pregnancy related visits because I have Medicare as well as BCBS or will I be able to use BCBS as primary and Medicare as secondary? Will BCBS cancel my coverage because I will be on Medicare? I have never been on Medicare so I have no clue how it would work. If anyone has any information or suggestions please let me know! 😊😊😊