I'm freaking out and will put as much detail as possible. But I need some form or closure for my situations, please!

My boyfriend and I had sex (my first time) around the beginning of December. We did not use protection, however, I am on the birth control pill and have taken it as directed. The next day I got Plan B, to be safe. The second time we did, I got the pill again (we then decided we should get condoms so I don't have to keep buying Plan B), and shortly after I got the spotting side effect of the after pill.

Fast forward, the third time we did it, we started, then put a condom on halfway through. Fourth time that month, we used a condom the entire time. Now it's January, fifth time we used a condom, sixth and final time we did not and I got a morning after pill the day after.

Lately though I have been having some weird things happen and I can't tell if it's stress, pill side effects, or pregnancy causing it. I have not gotten my period since the very beginning of December, first off. I have had irregular periods in the past, but I just think it's weird to have one in December, but as soon as I become sexually active, it stops. Second, I have had weird pains for the past 4-5 days constantly in my stomach and lower abdomen. Almost like cramps and stretching of muscles kind of pain. Throbs in my vaginal area are frequent as well.

I have not had any vomiting or other signs, but just today my breasts seemed a tiny bit tender. What could be causing these things to happen? The pain in my lower stomach and uterus area is more noticeable than not, constant as well. The last time I took plan b was 4-5 days ago.