What Causes Tiredness And Nausea Along With Delayed Periods?

Hi doc, i have a 9 months old son and i have been taking triphasils pills as contraceptive, but lately ive been feeling tired, nauseas and my period is delayed im on my third red pill and nothing yet, the question is could i be pregnant? if so is it safe to fall pregnant this soon as i had my son wit C section he is only 9months