When will my period come!?

So I'm 12 years old. I've been told that no one wants their period but I'm sick of having to wait. People say that you're supposed to start going through puberty a year or so before menstruation. But the thing is, I am in 7th grade. I started to grow breast buds in 4th grade. They are however, extremely small breasts. Hardly even noticeable. I don't know if thats a contributing factor, but I've been waiting for ages it seems. I also began growing pubic hair in 4th grade. It is very very thick now and it has been for about a year. I get pimples all the time, since 4th grade, once again. The odd thing is, I don't get cramps but I do get nausea. I get nausea and headaches quite a bit. I don't know if I have discharge as I've never checked. I am moody a lot. I get gas cramps quite commonly. I am about 88 pounds and I am 5' 2". I am no longer simply a stick, but I've actually grown a figure. My hips are wider and they curve in at the waist. When do you think my first period will occur, also considering the fact that my mother had hers when she was 13 and my sister had hers when she was 11. Please help! Think it through and don't jump to conclusions unless you know what you're talking about. Please! Thank you!