Pregnancy test

I had sex on August 12 and my fiance came inside of me. I want to be pregnant so I was happy. Other times since he has still pulled out. I have not have had my period since July 26th ish and I took a test today but it said it was negative. I think I might have held the test in my urine too long. Could this cause a negative result? I really do want to be pregnant but I would love to know for sure. Sorry for being so detailed but they do help in times like this. Thanks for any help in advance.