Help!! Implantation??

My last AF was jan 19th. I have a normal cycle every 27 days. I had intercourse jan27th. Glow said my cycle would be here feb14th but it wasnt. I started feeling nauseous and gassy so i took a pregnancy test fed18th, it came out negative. The same day i took the test i started having mild/slight cramps, i assumeD it was my AF so i thru on a pad. Hrs letter i go to check on it and there doesn't seem like a period was there at all. Just a little bit of brown stuff which is unusual cause i normally have an on time, heavy, excruciating pain AF. My mild cramps has stopped also. Could this be IB??