signs that indicate that im about to have my period

i havent started my peroid yet and i have:

cramps ( not very often tho)

heavy and light discharge(sometimes brown)( ive had it for like a few years and sometimes its really really heavy)

gooey clear stuff

very bad mood swings( like ill be all cheery and then the next its like i want to throw somebody off a cliff)

im 13 and most of my friends have statred. so if u could tell me when my period is gonna start or what this means id really appreciate it.