Feeling betrayed

I found out yesterday that my mum has been telling everyone my baby news. Not only do I feel robbed of my opportunity to share my happy news, but also it was mine to share not hers, I didn't tell people yet for a reason! Last year my beautiful baby boy was stillborn at 28 weeks. My family have not been supportive and one of my sisters actually stopped talking to me (cut me off) because she 'has her own stuff going on and I'm still going on about my baby' lovely girl! My other sister hasn't spoken to me other than to say 'thanks for letting her know' after I'd informed her of my sons birth. We never do really talk, it's been a strained relationship. However my mum has immediately told them both about my pregnancy 4 weeks in, I mean immediately! Feels like she's just gossiping about me. I'm now 13 weeks and feeling ready to tell, there's no one left to tell! I suffered a miscarriage after a year of ttc, after my precious baby died. Not only did my mum tell my sisters then (and then about my miscarriage a few days later), but then when I got pregnant again 3 months later and she did it again! She obviously knows she shouldn't be saying anything because she's kept it a secret from me! Not 'I've told Natalie and she's really thrilled for you' just secrets. Yet she couldn't keep my secret?! Neither sister has congratulated me or given their support after losing a second baby. So what's her motive? I feel betrayed by her.