I don't know if I could still be pregnant?

I am a week late for my period I have taken 3 pregnancy test On on the first day of a missed period and another on day 4 and the last in the morning on day 5. I do not have that many symptoms, I am a little More tired then normal, I am hungry all the time and well i haven't had a period, but I have had clear/white slimy watery discharge. I have heard stories of people who have been like 2 or 3 months before the urine test came out positive. I have never been late ever since i started having periods I have always been like clock work. I am not under any more stress then normal . i haven't gained weight and I don't think I have an illness. What else could cause my period to not come on time?? could i be pregnant?? How long should I wait to go to the doctors? (I do know that they ask you wait a little just in case)??? We have been trying to have a baby but at this point i just want to know whats gong on so I can either get my period over with and start trying Again or be excited I am pregnant. Thanks to anyone who can either give me information or stories if you had this problem and ended up pregnant.