OK well sounds like the biggest problem of your relationship was that he was a world class jerk!! Yes past issues can effect future relationships but its disgusting he used that as an excuse, as for emotional shields I think for them to truly work i think you would have had to already give up mentaly on everything so although it sucks we should embrace our emotions good or bad we have them for a reason, if we hide away we implode. I really hope your find someone who will treat you right hun wwish all the best.