Hi isnaughtafarm!
Welcome to the farmingfriends forum.
It isn't easy to tell if a pig is pregnant, although they will come back into cycle every 3 weeks if not pregnant.
If your soes are only 4-6 weeks away from having piglets then she should be looking rounder around the stomach, if they let you touch their tummy area then you may be able to feel the piglets moving, but this isn't easy to determine.
Their teat area will be enlarging as well.
When farrowing is imminent this is what to look out for.
When farrowing is imminent there are a number of signs to look out for.
# Restlessness. The sow or gilt will pace up and down or circle round and round.
# Nesting. The sow or gilt will pull or the bedding material into one area and create a nest. They do this by carrying the bedding in their mouths and moving the straw with their feet. This usually occurs on the day of farrowing and it is an amazing sight to see as all the bedding that was previously covering the barn floor will now all be neatly in a nest shape – this happened when Cagney, my Saddleback sow, had her first litter. I went in to feed her and she was laid on her nest and not one piece of straw was anywhere else in the barn!
# The size and shape of the stomach will increase before farrowing. I try to get into the habit of feeling the sow’s stomachs when I feed them so that I am aware of any changes in size and that the sows get used to me touching this area.
# The size of the mammary glands will increase as they bag up with milk. I also try to touch the teats so that the sows get used to me doing this so that I can check for milk production before the onset of farrowing.
# Milk production. Just before farrowing the sow or gilts milk will be released. You can check this by squeezing the teats and if milk droplets come out then farrowing is close.
# The vulva becomes larger and reddens. The muscles around this area slacken before farrowing takes place. This is not always easy to see to the untrained eye but once your gilt and sow has farrowed once or twice it is easier to identify. it’s amazing how often a pig breeder spends looking at the animals bottom!
# Laying down and stretching out the back legs will occur as farrowing begins. This is not always the case as some gilts and sows will stand to farrow. My saddleback sow Lacy did this when she was a gilt and had her first litter.
# Heavy breathing. As farrowing begins the gilt or sow will start to blow and puff as she strains.
http://farmingfriends.com/signs-of-a-farrowing-sow-or-gilt/
The farrowing process is an amazing sight to see.
Good luck and let us know how the pigs get on.
kind regards
sara @ farmingfriends