Two FALSE negative pregnancy tests?

I haven't had a period for almost 3 months. I'm on the pill, so when I do have a period it's very light and only lasts two days. my boyfriend and I always use condoms. I've been very very emotional here lately. my boobs are sore and are swollen. my back hurts all of the time. I wake up in the middle of the night nauseated but I never throw up. I took two pregnancy tests and they were both negative. any way that both of them could have been wrong?