My boyfriend denied trying for a baby

So I'm 8 weeks pregnant and over the moon. My boyfriend and I have wanted this for a while and have been actively trying to get pregnant...To the point of using an app to help detemine when im ovulating, and buying a sperm checker after a few months of trying to check everything was ok with his swimmers before going docs...obvs everything was fine since im preg now. 
Im furious with him at the moment though...He just told his sister, and when she asked him if we'd been trying he said no it just happened but he's happy. Am i wrong for being so hurt by him saying that? I just feel like it makes me look bad to his family. We've been together nearly 4 years. 
We both wanted this and were trying together so i dont understand why he would deny it regardless of whether he said he's happy about it or not. I dont understand why he couldnt just tell the truth that yes we were trying.