I feel so horrible??? Am I a terrible parent?

Babies at this age do not really understand pain and they are not dramatic when things happen. He was probably startled from the fall, and also if you freaked out or raised your voice when trying to grab him it could have scared him. He is fine, and accidents happen at this age. Now he knows what happens when he climbs all over things, so you need to remind him not to climb like that. It was a simple accident, it happens to the best of us. As long as your house is baby proofed, which your house seems pretty safe (no sharp corners or glass counter tops) it will be okay. As a precaution just always keep in mind the possibilities of an accident. Maybe you could rearrange the living room with blankets and things to have him a special play area and he will learn that that is his area to play. Don't be hard on yourself. Your child will react how you react, so for the future remember to stay calm. Worse accidents could happen in the future that aren't your fault, and its up to you to remain calm so that he isn't scared. You are his hero, and he looks to you to see how he should react.