Why do I always feel like I’m doing something wrong? I cry at the smallest things. I feel nobody cares

Wow...I can hear the pain you are feeling in your words as well as the sincere desire to change the way you feel. 

It is quite possible that your brain is responding with what we call "procedural memory", which is building a brain pathway similar to riding a bike.  Your brain has built a pathway for riding a bike so that now you are able to ride without thinking about balance or falling down.  In other words, you may be responding to a trigger from earlier in life where someone, or yourself, has strongly told you, or you have interpreted, that you must be or respond in a certain way and if you do not "act right", then you are not "good enough" or don't measure up somehow.  Sometimes, a person will set super high standards themselves and sometimes a parent or teacher demands "greater effort" or compares you with someone who performs "better."  It is not unusual for each of us to focus upon the negative, hurtful thoughts.  We all worry and speculate and engage with "what if".  Thinking negative thoughts (worry, speculation, assumptions) activates an area of your brain called the Amygdala which is involved with anxiety and depression.  Thinking about what is "true" (not positive thinking) helps put the brakes on anxiety and depression.  There is a procedure which can help build a new brain pathway that can extinguish the trigger leading to negative, hurtful thoughts and beliefs.  The new procedure takes practice just like learning to ride a bike but it will likely not take nearly as long to build a new brain pathway. 

It is also important to understand that you cannot please everyone...that is unattainable.  Plus, you are not responsible for how someone else behaves or responds.  If you had the power to control how someone behaves, wouldn't you choose a really good behavior?  Of course you would.  Their behavior is their responsibility, not yours.  Feeling as if their words/behaviors are your fault is a false assumption and not based upon truth.  Continue to be a loving, caring person who seeks to meet the needs of others, but care for yourself in an equally loving manner.