Hi Amy,
all women worry at the early stages, its natural. We spend the first 12 weeks and last 6 weeks constantly knicker checking lol
But you know that your body has produced a baby boy already so it ought to know what its doing, think of that.
If its any help to you you could also try joining this group of ladies, all expecting babies in March 2009 too.
http://messageboards.ivillage.co.uk/iv-ukpbmar 2009/
The ladies on here are great and full of advice too, but you may want to also talk to those who are at same stage of pregnancy as you are.