Help!! 14 days late


I need advise!! I am now 14 days late for getting my period, I was supposed to start the 28th and end the 4th. I have tested a few times the week I missed it, last week as well and now this week and all negative. I have been having slit spotting very very light (sorry tmi-only when I whip off and on) the past 3 days. But it will show at let's say noon and then I'll go back to the bathroom at 3 and theres nothing. Do i keep waiting to take more tests? Or make a doctor's appointment with my obgyn!!? We have been trying for about 4 months now to get pregnant and we already have a 2 1/2 year old daughter, we really want another but this is nothing like my first. I found out after 4 days of missing my period. Any suggestions?