missed birth-control, hot flashes, nausea. Pregnant?

My girlfriend is 20 years old and opn birth control. 2 weeks ago we had sex after she told me that she had missed two pills is a row the 2 days before. I may have had pre-cum inside of her. Now she is due to have her period any day, but has not missed. We had sex several times before but this was the only time that i felt like I may have cum inside of her. THis past week, she has had to hot-flashes where she gets really hot and sweatty, then cools down and gets really tired. I know this is caused by lack of estrogen, and I was wondering if her symptoms now are from missing 3 pills this month. The other morning this past week, she was blow-drying her hair(hot and uncomfortable environment) in the morning and suddenly had to vomit. We have not had sex since 2 weeks ago. Could she be pregnant? She does have acid reflux. She also refuses to eat red meat, but she eats well for a 120lb 5-4 20 yr old girl. He lifestyle is very stressful though. She works 8-5 and then goes to night school. Her father also just recenlty committed suicide is December. I think it might be affecting her subconsciously. A few questions, could she be anemic? Have diabetes? Pregnant? Could it all be because of birth control? Why does she have hot-flashes? Thanks