My secret miscarriage at 18. TRIGGER WARNING

In early January 2020 found out I was pregnant! I was about to turn 19 , living with my mom and boyfriend and it was pretty shocking. But, all I could think about was having a MC. At one point at around the 6 week mark all I could do was pray and cry because deep down inside I already knew. So fast forward a week or two and I had a super hectic night and of course that next day I started bleeding. I went numb all I could think about was how I already knew this was going to happen. So, fast forward to now my sister and I were looking through my memory books and there were the positive pregnancy tests. I snatched the book away and carried on looking at something else. My problem is she'll probably tell my mother. I didn't ever want anyone to know. My boyfriend and I were using protection so I wasn't being stupid. But I don't want to speak about it. I honestly just got over the huge hump of beating myself up about it and I personally don't think it's anyone's business. So, if my mom approaches me about it, What should I say to let her know I don't want to speak about it without coming off rude.