I Started My Period On September 21, Then August 15,

I started my period on September 21, then August 15, then today Nov. 11. If my calculations are correct, my period is late by 3-4 days and I have negative home pregnancy test results, and I am having very light bleeding. Can I still be pregnant? Please help. I'm getting frustrated and its stressing me out. I want a second child, but I feel as though its harder to conceive the second time around. Can I get an answer to my problem please.