Could this be pregnancy?

For the past couple of days my lower back has been hurting sooo bad! I have to take Advil. Me and my boyfriend had sex on 8/10 and 8/13 both in my fertile window. I get cramps and back pain like blood is bout to come out so I go to the bathroom and check and nothing. Could this be implantation camps? I have been urinating a lot as well. Im not suppose to come on my period until the 29th. Should i test or wait?