worried about having baby early

well i been having pains for the last 2 days, and preasure. i was 6 to 7 weeks early when i was born and my sister had her first baby 3 weeks early, i am just worried because i am only 30.5 weeks, i have a feeling that he is going to come early but i just want to be on the safe side, i dont want him to be to small, i go to the doctor wednesday and i go to my last birthing class tomorrow so i might ask then. i am still working almost 40 hours a week, i need to work i cant afford being off work plus they have not found anybody to fill my spot when i leave on maternity leave. if anybody has any advice let me know. i am feeling kyle move alot more so i am not sure what is going on, i try to relax when i get out of work