Hi,
you can get bladder weakness during pregnancy as the hormones that work on relaxing all your muscles etc also work on your pelvic floor muscles therefore they become weaker. Pelvic floor excercises will help and maybe buy some pads that are designed for bladder leakage as they have odour control and are designed to cope with urine as it has a faster flow than blood lost during your period eg: tena pads (the cheapest place i have found them is chemist warehouse). Maybe get a referral from your ob to a physio who specialises in urinary inconinence they will give you pelvic floor exercises and specific advice.
Try not to worry about it though it is pretty common during pregnancy and after having your baby.
Good luck