Help telling the in laws

So we found out we were pregnant a couple weeks ago after trying for nearly a year and having had a chemical and two miscarriages none of which my partners familh know about his sister also had a miscarriage the same time I was and she told me about it but I’m unsure on how I should tell his family without hurting his sister and most importantly I feel I should tell them everything but honestly don’t know how I was going to wait till 12 week scan but they keep mentioning that I look fatter and asking if I’m pregnant and I know you show earlier when you have already had a child I just need advice please as partner Alison doesn’t know how to say and when should we say currently nearly 7 weeks previous miscarriages were 4-5 weeks thanks