Hi, I have missed my period by around 4 weeks now, I had a pregnancy test 2 days ago that was positive :) and every test since is negative :( . I have been urinating more frequently sometimes without having a full bladder, I just fell like I need to go all the time. My nipples have become more sensitive and I've been feeling tired a little more at times. Has this happened to anyone and they still find that they are pregnant at a later date/time??

Sounds like you may be pregnant... maybe not, hard to say... I'd suggest it's time to go to a doctor and get a blood test for a definitive answer.