Someone please Help me here.

I keep geting shot at by SAMs to the point that I cant complete my missions. I can only carry a couple HARMs, the rest of the room I need so that I can carry bombs to hit my target. Are there any tips anyone can give me to avoid being fired at by multiple SAMs? Also when is it best to employ my ECM? I know I should not have it on all the time. Its just so frustrating to not even be able to reach my target due to the need of constintly evading SAMs, causing me to burn up all my fuel and using up all my chaff and flares.

Thanks for the help.