What Causes Bleeding And Cramping After Having An Intercourse?

Hi there was wondering if you could help, I have been bleeding in and off for 4 weeks now.. Mostly light pink, but after intercourse its bright red blood, almost like a period. I have also been cramping like I m on my period but I m not? Also on the left side of my upper stomach just under my breast has been going numb and has been pulsing like someone is punching me its not very painful, just uncomfortable! Can you please shed any light on this? My main worry is that it could be pregnancy related?? I would be very grateful to hear back from you, thanks.