well me and my boyfriend have had unprotected sex 4 times in the last 2-3 months and well in the last 2 months I have gotten 2 days late periods yet my period is very regular and about 28 days I was due March 4, 2013 and didn't get it until the 6th and I was then due the 6th and didn't get it until today which is the 8th yet I have not been feeling well these days I keep getting constant headaches, very sensitive nipples, slight back pains, cramping as well, nausea and my temperature has gone up a bit and well occurs with headaches. my point is can I be pregnant due to this? or am I pregnant? if not then what is causing all of this?