You are certainly not alone! The pregnancy shifted your bladder. This happens all the time (another joys of pregnancy!) so it sits a bit lower than it used to. The Uretha - the tube that connects your bladder to your opening- would traditionally kink when pressure was put on (like running, jumping, sneezing), think of a hose and when it is bent, no leakage. But since your "parts" have shifted, the kink doesn't neccessarily form to stop the urine leakage.
Speak to your doc about it. See a urologist or a gyn with this type of surgical experience.
Step 1: do kegles (sp?). Sounds simple but you must be persistant about it and do it all the time. This may be enough to correct your issues.
Step 2: Talk to your doc. You may need surgery. Now when I say surgery, I mean a small procedure where they can insert a little 'hammock' that goes under the uretha, so when pressure is put on your abdomine (like with a sneeze) and the bladder pushes down, the hammock with support the uretha and create that all important 'kink' in the hose.
I am scheduled for this same procedure since my pregnancy as I too have occassional issues with leakage that kegles did not help. Let me know if you need the name of a doc, I do recommend my Gyn as he is a surgeon with loads of experience in gyn/urology issues. He's proformed several minor surgeries - plus delivered my twins! So I do recommend him greatly.
Good luck, just know that you don't have to keep putting up with this. From everything I've been told and read, you'd need a 3 day weekend to recoup and then you're fine.
J.