I think it's doubtful that you are pregnant since it wouldn't be the right time in your cycle to conceive. But, I'm sure stranger things have happened.
I hope I'm not over-stepping here, and forgive me if I am, but if hubby doesn't want another child...would you really want to be pregnant? He decided to throw caution to the wind one time and I'm sure he would love your 3rd child to no end, but I guess I just feel it should be a decision that you make together and BOTH want.
And, I say that as someone with two boys and who wouldn't mind another baby. My husband (an amazing father) is absolutely done, though. I asked him just last week what he would do if I was pregnant and the look on his face was priceless. He really isn't ready for another one and most likely won't be.
Good luck and I hope that whatever the test shows in a couple of weeks, it's for the best!