In december i had unprotected sex on the 20th and the 27th, i did a pregnancy test 3-4 weeks later and again two days later and both were neg. But recently i have been feeling incredibly tired all the time and quite nautious. My 'periods' have been strange in consistency and colour, where they would usually be red in colour and very heavy with painful cramps etc they are very light, with barely  any cramping and light pink or brown in colour, it is  almost as though I am experiencing what is called spotting, could i be pregnant? Is it worth me going to he doctors/taking another pregnancy test or?