Just don't get it!

So, I've been married to my husband for nearly 7 years. We dated for 4 years before that. I have always felt like my mother in law has hated me. She never has kind words and always puts down any decision my husband and I make. We have adopted 3 children and she has never really treated them the same as her other grandchildren. Well, I finally got pregnant (she doesnt know about my 2 miscarriages) and told her on Mother's Day along with my mother. Ever since then, she has treated me completely different! She has made me shirts and is kind to me, and acts like she has finally accepted me. I just don't get it!!! Why now? Why not when we got married? Why not when we adopted our children? Why did I have to become pregnant before she finally decided I can be accepted as part of the family? 😞 I have struggled for so long to please her and gain her acceptance so I don't mean to complain. But it hurts! ALOT!