I am not quite sure…am I??

Here we goes…my last period was March 4 and I have never been late before. On March 28 I have spotting about a size of a penny of blood and that is all. This month it’s already April 22 and I haven’t even start my period yet. I been have sex with my boyfriend on a regularly basis unprotected for the last 2 years. I have already taken a pregnacy test a week ago and it turn out negative. I keep having these feeling like you were on your period but it been 2 week and nothing happen. Could I be pregnant and not knowing it…? I need help…