Why am I suddenly missing periods with negative HPTs?

I am 26. My periods are pretty much regular. At the most a couple days off here and there. They normally last 8 days (lucky me ugh). Aug sept n oct I had my normal 8 days all exactly on the 20th. Nov 24 I had one for 3 days. Jan 18th I had a very light one for 6 days. Very light. Feb 3rd I lightly spotted once. It's April now. I've taken every HPT on the shelf. The last of which this morning. All negative. I'm not stressed. I eat well. I'm otherwise healthy. Could I still be pregnant? Could menopause start this early? What else could be going on? Oh I also had a son 7 yrs ago 2 months premature, a miscarriage 5 yrs ago n a daughter 4 yrs ago full term. Thank you for reading all this!!