please make sure ur ob/gyn is aware of ir previous issue.. if u havent visit one do visit and let them know everything.. along with ur concern.. i would suggest following the doctors advice .make sure u dont take a lot of stress .. i know its easier said than done but stress definitely wont help you..
Has your ObGyn suggested cerclage? That would require some bed rest. But, depending on the nature of your work, you may be able to safely resume after an appropriate time.