Birth control

I started a new birth control and when I switched over I hadn't taken any BC for a few days and my boyfriend ejaculated inside me. My period should be here tomorrow but I've had a lot of nausea and diarrhea and headaches, eating more, somewhat tender breasts and some more symptoms and although some of these are common when starting a new birth control it seems way more extreme than I've ever experienced and I also started vomiting though and I have really bad back pain/cramps for a week now with no blood. Could it be pregnancy or just getting used to the new hormones?

I did miss a couple. I was on the old birth control placebos and then I didn't start the new pack immediately I waited honestly like a week to start the new one and it was the week right after my period. I've also had a bit of heartburn which I've never gotten before. But normally when I'm not on birth control my periods are extremely irregular and I won't have it for 4 months then when I do it'll be for two weeks so I'm not even sure if I ovulate normally off the pill.

I didn't start it when I should have. I was a week late taking an active pill. And it has higher progestin and lower estrogen. The doctor didn't tell me what to expect or when to start it or anything.

I did know that but honestly I didn't think about it and that's my fault and I'm not terribly worried about it because my boyfriend and I have been together for three years and talking about marriage and children. We could finically raise a baby but we're both still really young (both 19, he's about to turn 20) and I don't think we're ready for a child but if it happened we could do it.