Delayed Period With Dark Blood, Lots Of Clots After Unprotected Sex. Implantation Bleeding?

My last period was feb. 14th, normal- 8 days, light then heavy then light. I started spotting on march 10th, it was once, when i wiped, nothing after that. was supposed to get my period march 16 or 17th. never came. then i started having some brown blood on the 20th, 3 days late, and its not fresh blood like normal, its like dark red/ brown, and really stringy. with zero cramps . its now day 2 and i still have light, stringy, only when i go to the bathroom. i had unprotected sex around the 19th of feb, is this my period being late? or is this even blood? theres no tissue , its all dark red and stringy, clots. normally im very crampy the first two days, and bright red. not this time. no cramps. just dark blood and lots of clots