How true is the ring trick for telling the gender?

I did the ring on a string over my wrist a few times now and its supposed to pick up the births you already have as well. I have 2 boys now and miscarried last yr at 2 months. When I do the ring it went back and forth 2x for both my boys then in circles 2x perhaps the child I lost was a girl and i'm wondering if i'm having a girl now. I have done this many times infront of my family and then my fiance. I used my ring as well as his class ring which is heavy and it did the same thing. I also have checked the chinese lunar calendar and it says girl plus I done old wives tale quizzes and it comes up girl. Yes i'm really hoping for a girl, but I don't want my hopes to be crushed. Do you think its possible that i'm having a girl?