Late and confused

Sophie
I have been trying to get pregnant but been really busy with home life and work that I forgot I was due on my period. I realised I was a day late so did a test but I was negative! I am normally regular never had a late period since the twins (2years).
I have had low abdomen pain, more like an ache not really period pains. Now I'm 5 days late I did a test this morning and still saying negative. I have been so tired and have no energy. I am so confused I dunno if I am and it's really too early to tell or I'm going to have my period?