Teenager. Brown Discharge, Cramps, Headache, Public Hair, Weight Gain. Time For Menstruation?

Hi !
I'm 13 years old. I have so much discharge every day that I often need to wear a pantyliner. I've experienced spotting a few times now like 5 days in 2 weeks. I already noticed brown discharge. It happened 3 times this week. I have a lot of pubic hair but there is still a little space to be filled. I have a lot of armpit hair but it's mostly blonde with some black ones. I have spiky leg hair and quite a lot of arm hair. I gained weight in the past year. Last year I weighed 31.5 kgs and now I weigh 42 kgs. Last year I was 144.5 cm tall but this year I am 152.8 cm tall. I often get cramps in these places: my lower stomach, my lower back, my legs and I also get headaches very often. These cramps have been happening for a few months now. Is my period on her way? How much time is there till she comes? Will it happen this month? Is it normal to want your period but sometimes when you think abou it you don't really want it? What do you think?