Please comment- bad pains

Pip • Pregnant with a little boy • c-section is booked for 4th July 2016 at 8am ✨
For the past few days everytime me and my boyfriend have sex, I get this cramping, it's like period pain badly. It last for a few minutes and then disappears? I was due on today and still haven't came on. I was sick last night and not feeling myself. Please comment.