cramping and confused!

so I have been having some symptoms that make my boyfriend and I think I my be pregnant. little spurts of nausea and feeling really tired are the main ones. I was suppose to start my period yesterday and it hasn't came yet so needless to say we have been really excited. I haven't tested yet because my boyfriend has been out of town for work and he really wants to be here when I take the test (he comes home Monday which is when we plan to test) but today I started cramping which got me worried that my period may be coming :( I have never experienced "implantation cramping" and don't know the time frame that that is suppose to take place. can someone tell me how to tell the difference between the two types of cramping. I'm freaking out at the thought of my period coming after we were so sure I could be pregnant.