Maybe pregnant?

So my boyfriend and I are trying to get pregnant but my periods are very irregular. We had sex towards the end of my last period (on the 10th and the 13th.) I am not really sure when I ovulate because of the irregularities. Since about the 18th I've been nauseous every day, and I had spotting yesterday (the 21st) could morning sickness and implantation bleeding happen that quick? Has anyone had this happen and been pregnant? Should I take a test?