could implantion bleeding happen the next day after unprotected sex

:$ ok well my husband and I have been ttc for 5 months and last moday we had sex w/o a condom twice that morning..(I was ovulating that sunday)tue I woke up and went to the bathroom and there was a brownish colored discharge on the tissue. Later on that day it was gone when I woke up the next morning it had returned...the last couple days I have been spottin very lightly. not like my reg. Period I usually get bad cramps but this time there were none and it usally starts off heavy..it has got a little heavier brown/red discharge...but its def. Not normal...this morning I woke up and I had to vomit...I need your help a.s.a.p do u think I might be preg.?????,