As a young man growing up inside his father's starfighter simulators, Andy got to be pretty proficient behind the stick. His father was always out on delivery runs, so he didn't notice that Andy had a knack for flying, and thus never asked him to help with supply runs because he never felt that Andy would like it. So Andy stayed in the sims, getting better and better.
On Andy's 18th birthday, his father gave him enough money to buy himself a freighter, thinking he would help out in the family business. That is exactly what he did. He went out and bought a Corellian Y2-1200. Of course it wasn't the best one there, but Andy wanted to try to fix it up and modify it as he wished.
As soon as he had it fit to fly, he helped his father runs supplies, and they began to learn to fly together well. As time went on, Andy added little gadgets and such to his freighter, which he had already named "The Shooting Star". His father and himself ran more and more missions, and knew that a tangle with Imperial forces would not be a problem, as long as they could always run if things went bad.
Time passed, and Andy now found himself at 21 years of age. His father and himself got caught in a scrap with the Imps, and were vastly outnumbered. They needed to run to the nearest nav buoy, which was 20 klicks away. At the very instant that the Imperial fighters converged upon them, Rebel fighters started to pour into the system. The X-wings hit the fighters by surprise, and the Y-wings destroyed the Imperial Star Destroyers. The Rebels ask them if they would like to run supplies for the Rebel Alliance. Not seeing that there was much choice, Andy and his father agreed to run supplies.
Andy and his father ran supplies to a new Rebel base, on the ice planet of Hoth. While on the downtime, the Rebels discovered an Imperial probe on the planet. This alerted them, and they started to evacuate. The Rebels also commandeered Andy's and his father's ships to help. Of course, they were allowed to fly their own freighters, they just had to carry supplies and personnel off of Hoth.
Andy and his father were cleared to go together without an escort off of the planet. The ion cannon blasted behind them, and hit the Star Destroyer directly ahead of them. His father reported over the comm that he was having trouble, and Andy whipped around just in time to see his father's demise. A piece of TIE Fighter debris clipped his father's engines, rendering him powerless. Then another TIE Fighter flew in and picked up the easy kill.
The anger inside of Andy made him explode with hatred. He flew with the knowledge that he had nothing left in the universe, so he had nothing to lose, not even his life. Andy maneuvered in and out of TIE Fighter formations, provoking multiple targets for his gunners. This was about the time when another transport was exiting the atmosphere. The TIE Fighters started to swarm it. Andy got there just in time to vape the TIEs, and escorted the transport to the rendezvous.
While unloading the personnel he was carrying, the crew of the transport he saved thanked him graciously. One even called him a bulldog for being so tenacious. A Rebel pilot overheard that comment, and came over to suggest that Andy join his squadron. Of course, Andy accepted, seeing this a way to hurt the Empire and exact revenge for his father.
While they were on a mission, the pilot who recruited him called him "Bulldog" to get his attention. Of course, the other pilots heard the comment and started to call him Bulldog also. Andy liked the name, and it stuck. Andy likes to fly, but his squadron always seems to be stationed on some backwater planet with absolutely no action. So he puts in a request to join Corsair Squadron, onboard the Liberty.