unusual irregular periods please help

Ok so I am 24 and conceived my first when I was 21 with only 1 try. I have never had irregular periods until this year. I had a period January and then didn't have another till April and now again I still haven't had one since April. I've taken pregnancy tests and we aren't pregnant. We have been trying since febuary to have a baby but then all this started happening so it's like I get my hopes up each month and then nothing. Has anyone ever experienced this?