I'm having that odd nauseous feeling again

While you would think I should know without taking a test, being I've been pregnant 4 times with 3 children - the youngest only 11wks old... I'm having that odd nauseous feeling again! My husband & I have only had sex twice since our daughter was born, the 1st time when she was 7wks. I had only had my 6wk check 4days before & the depo-provera shot the same day. My doctor did tell us to use a condom for the following 2wks as the injection isn't effective immediately. Which we did not do. I have spotted virtually every day since, but being that I don't think it was a real period I can't use it as a guide for anything. How do I determine if I am pregnant & how far I am without doing a test? I'm guessing about 3-5wks if I am. My husband is going to freak if I am. Mind you I will too.... Any advice would help. Thanks.