I agree with Stevie G, sounds like she might be pregnant
If he's been with her for 9 weeks/3 seasons you've still got around 6 weeks to go, but it's usually just in the last 4 weeks or so that the udder grows and the vulva swells. Providing the boar's doing his job and she's young and in good condition, it usually happens first or second time round
What date did the boar go in with her ?
Have a look at her side on and see if there's a diagonal line running from her back end forwards - there's a photo of one of my pregnant Large Black sows here
http://yonderton-com.webs.com/apps/photos/photo?photoid=154096226 where you can see what I mean, the pig in the background on the left is a pregnant gilt, around 4 weeks from farrowing and you can see the line on her too
If she looks like this, get a farrowing pen sorted and get ready
HTH
Karen