could i be pregnant? please help!

my last period was Dec 9th and ended on the 14th, i was fertile on the 21st but we also had sexual on the 9th, 16th and 21st. i have 3 period apps and they say i’m 3-5 days late on my period. i have an irregular cycle so i’m not trying to get my hopes up but today when i was at work and had like a half hour left of work i became so nauseous and lightheaded i turned completely red like i had a fever. i bought the clear blue test but i’m nervous to take it cause what if i get that negative 😔 i have a 5 year old little girl. i have bad cramps, back ache, sore boobs and still no period. would i be able to test now or is it too early?