Menstruation

Weird question ..

I didn't get my period for like 7 months and then last month it came out of no where so I got this app to track when it would come and it says it was supposed to come yesterday but it hasn't shown up I'm nauseas and have bad cramps , sore breast and bad back pain . I also woke up with a fever today is there any chance that the fever could come from my period coming , also any tips for regulating your period since I haven't gotten mine in so long .. thank you 🥰.