Usually if you have bleeding with passing of clots, it is indicative of shedding of the uterine lining, which would indicate pregnancy did not occur. Implantation bleeding happens to only some women, usually as a single episode of either brown spotting or a drop or two of bright blood lasting no longer than a few hrs at most and occurring 5-10 days after conception. It is unlikely that you are pregnant unless you have had unprotected intercourse since the bleeding. If it has been 4 wks since the bleeding episode then a home pregnancy test should show a concrete +/-. Good luck to you.