I may be pregnant. Im not sure.

OK so the last week of April I had sex with my bf and he came in me. Since last Sunday my great have been sore and my back has been hurting. I have several menstrual apps in my phone and they tell me my cycle was supposed to start yesterday or today. I haven't had a cramp all day and I've been unbelievably constipated. I want to take a test but I don't know