late period , baby 9 months

My little boy will be 9 months next week.I exclusively   breastfed till around 6 months and then only breastfed if he woke in the night. I started getting regular periods again, and I no longer breast feed at all as he sleeps through, this month I'm currently 4 days late and I've never been late apart from when pregnant. I've tested twice and it's negative and with my little boy I got a positive the day before a missed period. Has anyone had this happen before? 

I'm a nightmare and google everything and I'm now worried I'm having early menopause ! I'm only 25 ! 

Thankyou x