My periods came in jan at the beginning and the end. and on feb i did not see my periods at all the home pregnancy test came neg, could i be preg?

Possible: Any time you have unprotected sex, there is a chance for pregnancy. Best way to avoid (unless pregnancy is the goal) is to use a barrier method of birth control along with hormonal (if indicated). Of course unprotected sex can also cause forever-there std's that are not fun. To find out for sure, get another good home pregnancy test and use a first morning specimen for best results.