Could I have actually conceived this cycle?

Brittany • Happily married stay at home mother of 3
I am having early symptoms of pregnancy bad low back pain and ache feeling pelvic pain nausea off and on mostly after I eat I can't stand the smell of cigarette smoke I feel like I will throw up even if it's just on someone's clothes having indigestion and etc at suppose to start the 18th I'm very regular on my cycle could I actually be pregnant right now and not know it??