Recently, I've been peeing non stop. I thought maybe it's a UTI. Because I'd have to pee really bad and almost pee on myself i don't hurry. Today I've had some upset stomach/nausea and woke up with a major migraine. While at work this afternoon, I was so annoyed and just LAZY! Is this just a coincidence or is it very possible to be pregnant? Not too familiar with pregnancy signs. PLEASE HELP. (Especially if you've been pregnant before *for more accurate answers*) 

PS. Me and my SO use the withdrawal method and no other form of birth control