Confused! Please HELP!!

Katie • Me and my husband has been together since 2010/2011 and we been married for about 3 months and we are TTC and my body is being very difficult about it! But we would love to have a little baby!
I am about 4 1/2 weeks late on my cycle. I have taken PT and they have been negative. Should I wait a little longer before going to Dr. Or take another PT next week. Please comment your opinions! It would be greatly appreciated!