Have Heavy Period, Abdominal Pain, Dizziness. On Pill. Had Unsafe Sex. What Could It Be?

Helloo please may I ask you a query on my health problem? What it is, is I have been having heavy periods since i first started them when i was younger. I am 17 years old have a fiance and i am sexualy active. I can t even remember when my last period was. It wud of been about 2 month ago or coming up to be that. I was on the pill . It was the one you took all the time. I started it when i was already on my period and i took it for nearly a month maybe even longer. And i started spotting. I spotted for 3 weeks and i stopped taking the pill then i still spotted for another week. Whilst taking the pill i did miss 3 or 4. And i do have unprotected sex. But its been about 2 months and i haven t had a period. Last week i took ill, i was getting bad heads, dizzy, i felt sick and i was sick. Since then ive been getting the odd dizzy spells, i get proper bad pains in my abonminal if not in my stomach . I sometimes find that when im standing i need to sit because my back is hurting. But i have a bad back after damaging it a number of times. But i have started to eat a lot more and i noticed as well that wen i was spotting and even after i was constipated and didnt go for about a week or so. I don t know what s going on, but im just sick of the dizzy spells and the pains as well. What could it be?