I am sorry for your situation; you are not the first new owner caught out by bad information.
Most baby boys are coming into their sexual majority between 4-6 weeks, but there is always the occasional early one, so you may have just got away with it if you are lucky.
Your sows cannot be more than about 2 weeks pregnant and won't show yet in any case! What you are witnessing is nutrients finally going toward mummy's body instead towards her babies.
Sadly, you will have to do what every rescue does with sows from a doubtful/unknown source - keep a ten week pregnancy watch! Please weigh your girls weekly (which is a good habit anyway, as you can pick up any weight loss/illness early). Any weight gain over 30/50g is suspect. Usually, you won't be able see much until the second half of the pregnancy. Here is more on pregnancy etc.
http://www.guinealynx.info/reproduction.html also read up links faq and labor
The earliest signs are increased thirst, increasing weight gain and nipples elongating and swelling. Please make sure that you give any suspect sow double the amount of vitamin C in veg high in it.
Here are is a list of veg high in vitamin C:
http://www.theguineapigforum.co.uk/showthread.php?t=42
During the second half of the pregnancy, you also should add alfalfa hay to you timothy hay to cover the increased need for calcium for the pups' bones.
Please do not overfeed your potnetial mums - big babies in a small litter can cause problems at birth. The ideal diet is umlimited good quality hay (up to 80% of the daily intake), unlimited pellets for piggies under 6-9 months and then slowly reduced to one handful per adult piggy per day or less, 1 cupful/50g of mixed veg per piggy per day in however many servings you like.
http://www.theguineapigforum.co.uk/showthread.php?t=37030
I wish you the best of luck! Please keep us posted and don't hesitate to ask any questions you may have.
You also might like to have a good browse around the forum, epsecially our reference section and the permanent threads at the top of the other section; they are all full of information.