Why am i moody all the time?

I am 23 years old. People would describe me as a fun loving loud gal. But the people that are close to me like my family and boyfriend would describe me as moody and snappy. I dont know why im always moody with people around me? i shout at my younger sisters all the time, its got to the point where they are scared to talk up to me. I feel guilty for my behaviour, i love my family and boyfriend to bits. I had an abortion when i was 16 then another abortion when i was 17, i never really spoke to anyone about it. My boyfriend at the time was useless, he never wanted to talk about it. I left school at the age of 15 with no gcse beacuse i got bullied so much i couldnt go back to school. i am now working at a bank. i feel my life is complete i met this wonderful man, who i will be marrying next year. but somhow i feel incomplete, i feel like i lost out on alot. can my past be troubling me? if so, where can i get help. i dont want to be miserable forever, i want happiness in my life.