Strange period is back

So as unbelievable as I find it, I haven't had a period in 41 days. There was very very light spotting at one point but that was it and I'm fairly certain my period is coming up now (sore breasts -.- always reminding me) but I'm worried about these large gaps. 

My grandma had a problem where she didn't have periods. As in her body would do everything right, except it wouldn't toss out the vaginal lining it'd keep it in there. She had to go to a doctor several times to get it all worked out. I'm worried about having something like that, and if it were to happen would it be a progressive thing where it dwindles to nothing or suddenly BOOM nothing.