Am I Pregnant???

I was recently married. My husband and I are not financially ready for children just yet, so we have been using the following methods: condoms with spermicidal lubricant, birth control pills, and withdrawal before ejaculation. However, I have become concerned lately when I noticed that my are noticeably larger and heavier than before, and have a different consistency (if that makes sense) and that my are sore. I've been really irritable and fatigued, and have frequent headaches, lower back pain, and cramps sort of like menstrual cramps, but not. Due to medical problems, my periods are very irregular, and it's been since February 14 since my last one, but I'm not sure if the irregularity is due to medical reasons, or if it's because I'm pregnant? Is that even possible with all of the precautions we've taken? If so, how likely is it that I am pregnant? I'd really appreciate any relevant input here...