It sounds like it is your pelvic floor Pontypine. Start doing those pelvic floor exercises religiously and speak to your GP/midwive about it. Also - make sure your bladder is totally empty when you go ot the loo by jiggling backwards and forwards at the end to get any last bit of leakage out and invest in some TENA pads. With plenty of pelvic floor exercise, am sure it will improve...
I think extended periods of sneezing/coughing can weaken the pf further.
How many weeks are you?
This is my 2nd pregnancy over a hayfever season. I find tightening my pf muscles when I sneeze helps - but this is difficult when you sneeze a few times in a row! It is a good reminder to do my pf exercises though!