Help!! What's going on?

So I've been having really irregular cycles for the past 3 months. Usually, my cycle is about 30 days, but lately, it has been extending for 40 days or so, and my period just doesn't come when it should. This has never happened to me before! I know periods can be up to 15 days late, but it just seems weird to me that this happens 3 months straight. Does anyone have an idea of what could it be?

P.S: I do have a boyfriend, but I've never had sex with him, so I know I'm not pregnant haha.