(NSFW) Am I too old for this type of "growth spurt?"?

I am fairly positive my breasts are growing. For the last couple of months they have been very sore off and on, with a deep aching sensation at times. My bras have become tighter and ill-fitting, while the rest of my clothes fit the same. I haven’t gained any weight, but my breasts look bigger.

Obviously I recognize that this is a sign of pregnancy, but there has been an absence of intimate activity in my relationship recently. My last 2 periods have come and gone on schedule, and I took two at-home tests just to be certain, both of which were negative. I have no reason to think that I’m pregnant.

I am 29, so I’m long past puberty. My cycle is normal and I don’t have any other “symptoms” or strange goings on. Am I crazy? Can this happen? Should I be worried?