Cramps and spotting

Okay so like two weeks ago I had unprotected sex and like a day or two had passed and I started spotting ones a day for five days and it went away and now today I never had this problem before but all day I've been getting cramps on my buttocks and lower back whole I'm sitting down and I end up having to lay down so the pain could go away. Can anyone tell me if this is a sign of pregnancy? Usually I take pregnancy tests if I assume I'm pregnant but usually the tests shows I'm not so that's why I'm not really planning on taking a test anymore when I assume things. Help please.