Telling mom

So my sister had 2 babies out of wedlock and the 2&3 baby was with her now husband. She told my mom about all of them in the middle of church and it honestly ruined their relationship. Now I'm 20 and pregnant with my 2 year relationship boyfriend. We've been living together for about 7 months now and I see my mom atleast 2-3 a week. It's so hard acting like I'm not pregnant! Especially when she takes me clothes shopping and I'm bloating like a mf. Any advice on how to tell her but keep our relationship? We just got back talking. My anxiety ruined our relationship for a long time.