When you've "had it bad," it means you've experienced something particularly difficult, frustrating, or upsetting. This phrase implies a deep level of discontent or discomfort, and there are a number of synonyms that capture the same sentiment. For example, you might say you've "endured a lot," "struggled immensely," or "been through the wringer." Other options include "been at the end of your rope," "been pushed to your limits," or "had a rough time." Regardless of which phrase you choose, the important thing is to communicate the severity of your experience and to express your willingness to move forward in a positive direction.