How Long After Having Pregnancy Symptoms Can Pregnancy Test Be Taken?

i am wondering if I could be pregnant me and my now ex has had unprotected sex a lot in December well I got my period in January but it was only 3 and half days compared to the normal 5 I never told him it was shorter so he waited to have sex with me on day 5 that night and it was unprotected. I have been feeling really strange lately like the things I like to eat I cant stand the smell of them or when I try to eat my stomach gets upset. I don't know what to do because I wont get my period again until the beginning of February. I don't want to tell him because he is moving out and I don't want him to feel like he has to stay and feel trapped because I might be pregnant. when should I take a test? and could I have been pregnant in december