My bubble has been burst...

So I've been having breast tenderness since Sunday or Monday and I was hoping it was a good thing. I know you can have that as soon as a few days after conception, but it can also be birth control pills or your period about to start. Mine usually start hurting a week before I start, so I was hopeful it meant the conception thing. Until a few minutes ago when I decided to look up the side effects for Prometrium, the medication I'm taking every night to thicken the uterine lining for implantation. And one of the most common side effects: breast tenderness. Lovely. I wish I had never looked it up. I wasn't having any weird side effects that I didn't already know about, so why did I go looking for info? Blah.