Agitation Towards Boyfriend

I've been with my boyfriend for 1 year and over the past 2 months I find myself frequently and easily becoming agitated and irritated with my boyfriend. Things I used to find endearing and cute about him now annoy me. I find that I become moody around him and it's not even because he's done something wrong. I feel really bad because he's so good to me, even when I'm in a bad mood. I still love him dearly, and he is truly the best boyfriend ever. Any advice on how I can work through this? Have any of you ladies gone through this with your partner?