Symptoms one week after conception?

Today at work I began crying uncontrollably and could not get hold of myself. This is very unlike me and my boss sent me home thinking it was the stress of the job getting to me. Some of my girlfriends/coworkers immediately said, "um... Are you pregnant???" I guess because it was so unlike me. I continued to feel super emotional off and on and really didn't know why for the rest of the day and into the evening. I realized this super emotional feeling actually started the night before, so it's been going on for like 24 hours now off and on. pregnancy test came back negative this afternoon but I'm wondering if it might just be too early to show up on an in-home test? I don't think I could be more than a week past conception... How early did others experience symptoms?