Chances of conceiving?

me and my boyfriend had sex last week on Jan 18,19,20 and 21. i ovulated between Jan 20th n 22nd. whats my chances of conceiving a baby? i been on pre-natal vitamins since last month. we been trying since aug-sept of 2010. if i am pregnant,when would i start getting pregnancy symptoms? and when should i take a home pregnancy test? im suppose to get my period on Feb 6