Have i done some damage to my back, should i see my GP or see how it goes?

a week ago i was walking down the stairs with my son when i slipped and fell right on my bum really hard!! dont laugh! lol, anyway for the first 5 days its been really hard moving around, going upstairs and carrying things as i would keep having pinching pains and obviously its bruised! anyway it eased off yesterday and asnt as bad but i was carrying my son upstairs and i got that sharp pinching pain again at the bottom of my back and it was quite painful for a few hours later and i couldnt lie on my back in bed! also (probably for women) if i pull n my mucles as in holding in a wee (pelvic floor) its painfull and i cant do it all the way, could i have done some damage? i have been taking paracetemol and iburophen which does help a bit..x