My honda wont start 2000 honda accord v.6 3.0vtec

i have a 2000 honda accord v.6 3.0 vtec coupe and it wont start..ive changed the battery twice and had my alternator checked and came back as fine once i cleaned the corrosion off the battery it seems to run smooth for 7 days..went out to start it crank but seemed like the engine didn't kick over..so it seems like the only way to get it started and going is by jumping it.once im at my destination and turn my car off it will start but it feels like the car putts/shakes then dies out my rpms will drop no matter how much i pump the gas peddle..once in awhile it will start but it seems as if jumping it is the only way...my battery appears to have power my alternator was said to be fine by auto zone..maybe starter??idk