Hi Deb, I know this is an older post but maybe I can help a little. I've gone through that too, and I've been reading thirty years. The feeling is not coming from you if you can't read someone. Sometimes consiously or subconsciously either a person is afraid to find something out, or they are afraid their secret will be let out. Know what I mean?
People tend to put up a defense, a wall, between you and them, sometimes they may not even be aware of it themselves, its a subconscious thing.
Usually when I hit a wall, i'll let them know I cannot read for them because they are blocking me. Sometimes they'll accept this and relax a little after I gain their trust, other times it is impossible. It is noone's fault, it just can't be done. It is psychic protection.
Let me give you an example, i'll use psychic healing . I can help people who live in far away countries to heal or at least be more comfortable if they want to be healed. I have even healed my mother who doesn't believe in these things. On the other hand, my boyfriend has ms, I've tried to heal him, but he won't let me in. He blocks me. I've asked people to pray in prayer groups, reiki masters, anyone i can think of to help in this matter. He blocks everyone. Why? Because his illness is his crutch, its the poor me syndrome. Thats what I mean when I say it isn't you when you can't read others sometimes. It happens for a reason, and they may not even be aware of it. In the spirit world, you cannot invade other peoples space and force your way in.Thats why I can't heal Warren But when the time is right sometime in the future, it may be different. Don't worry you are very good!

I hope this has helped a little.
Samantha